The Size and Depth of Arabic Vocabulary among Students in Malaysia's Selangor Religious Secondary Schools

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Introduction
Arabic language in Malaysia is known as a foreign language or a third language (B3), such as Japanese, French, German, and Mandarin. The status of the Arabic language is clearly stated in the Education Act 1996 (Ministry of Education Malaysia, 2013 Learning a foreign language is frequently hampered by issues like a lack of resources, a lack of suitable textbooks, less experienced teachers, low student participation in class, an unfavourable learning environment, insufficient vocabulary, and a heavy reliance on translation software (Mat & Goh, 2010;Rosli et al., 2022). These issues show that the process of learning and mastering B3 requires a long time, a lot of language input and communication interactions, and an active learning environment (Blake, 2008).
Based on previous studies, the level of mastery of Arabic and Arabic vocabulary among students in Malaysia is at a weak and limited level (Hunaidu & Sabae, 2019;Muhaimin, 2020;Rizan & Baharudin, 2021;Samah, 2012;Zaid et al., 2019). Language researchers agreed that the level of mastery of Arabic and English vocabulary among students is less than satisfactory (Jasni & Zainal, 2020;Muhaimin, 2020), and the use of memorization techniques in learning is seen as less effective. Therefore, this study is expected to add a new dimension to learning Arabic in the Malaysian education system.
Additionally, students have a hard time remembering Arabic language when teachers use fewer inventive and imaginative teaching strategies. Students lose motivation to study the language when textbooks are overloaded with learning content (Sari et al., 2019). Students also feel bored, are less effective, and think learning Arabic is challenging due to the paucity of Arabic media and the heavy reliance on textbooks as a learning tool (Natsir et al., 2021). In actuality, acquiring a significant amount of vocabulary is a key component of language development (Razak, 2018). This study aims to measure the breadth and depth of Arabic vocabulary knowledge among secondary religious school students.

Literature Review Vocabulary Studies
Vocabulary is crucial to learning Arabic since it can be used to combine a few additional words to construct a whole sentence. Irnawati (2019); Isnaini (2020) defined vocabulary according to the Indonesian dictionary, which is "perbendaharaan kata," or in Arabic, "mufradat". Diamond and Gutlohn (2006) perceived vocabulary as knowledge about words and the meaning of words. A combination of words that will eventually form a sentence and develop a language, according to Maskor and Baharudin (2020), is referred to as a vocabulary. A person's ability to utilise a language can be impacted by their vocabulary, making it a crucial component to consider when evaluating someone's proficiency in a foreign language (Fatdha & Wahyuni, 2018). In contrast, Role et al (1976); Schunk et al (1997) asserted that vocabulary is the key of language. They believe that the first step in learning Arabic is to master the language's grammar. The meaning of words will be impacted by grammatical errors.
However, grammar and vocabulary are two crucial components of language that are intimately related, particularly in Arabic. The development of an Arabic vocabulary benefits greatly from in-depth knowledge of morphology and syntax. Thus, students who master vocabulary will be able to match the words they understand by using correct grammar. Toiemah (1989), when discussing the teaching and learning of vocabulary and its importance, asserted that the main basis for learning a second language is through vocabulary mastery. al-Naqah (1985) supported the statement by discussing the importance of vocabulary mastery, which is the first step in learning a foreign language. This shows that vocabulary becomes both a tool that carries meaning and a method for thinking.
According to Wulandari (2021), who conducted a study on the perception of students who learn vocabulary through games, vocabulary involves all of a person's language skills. Vocabulary helps a person express ideas and views while helping them listen and read a sentence clause with a deeper understanding. The study interviewed 10 participants, and the results reveal that everyone responded favourably to the usage of games to aid in vocabulary learning. Among the reasons given by most participants is that the method used is fun, makes them easily remember and understand learning, trains students to solve learning problems, and reduces student learning stress.
Many studies conducted by past researchers are closely related to the level of vocabulary mastery. Among them, the study conducted by Ridha et al (2022) is about the use of animated videos that aim to stimulate students' English vocabulary learning in Iraq-Erbil. The use of animated videos in learning English produces diverse learning patterns, an interesting learning environment, and is a good support tool for the students' vocabulary learning process. His research findings found that most students in private institutions in Iraq-Erbil have equal and moderate vocabulary knowledge based on the pre-test conducted. Meanwhile, a study conducted by Hunaidu and Sabae (2019) on vocabulary mastery found that Arabic vocabulary mastery is still not at an optimal level. Their findings show that there is no indicator related to students' vocabulary mastery that includes active, productive, or passive receptive vocabulary.
Robin et al (2020) conducted a case study of children's mastery of Malay vocabulary. Their study sample consisted of two children and a teacher. The researchers used observation forms to record the vocabulary mastered and spoken by the children. Preliminary findings show that the level of Malay proficiency of Iban children at pre-school was weak. While the findings after the use of the Didi and Friends Song show an increase in vocabulary mastery among the study sample.
Additionally, a study by Akla (2022) emphasised the narrative strategy as a means of assisting youngsters who are not native Arabic speakers in increasing their vocabulary. According to the study's findings, kids strove to mimic every word their teacher spoke until they got it right. In a study where good emotions outweighed negative emotions, children's positive emotions were also found to be important. Students' negative emotions only resulted from poor class management and did not involve vocabulary learning.
Vocabulary, which is a collection of words that make up a language, is essential for mastering the four foundational abilities of reading, listening, writing, and speaking (Alam & Khotimah, 2021). Thus, vocabulary is a core aspect of a language, and language skill proficiency is highly dependent on mastering a large vocabulary and understanding its meaning (Baharudin & Ismail, 2016;Kuleli, 2015;Lemmouh, 2010;Samah, 2013;Maskor & Baharudin, 2020). Language learning becomes ineffective by only mastering the aspect of vocabulary size and depth. Knowledge of the meaning of vocabulary and how it is widely used in the right situation and context is a measure of the level of competence in mastering a foreign language.

Vocabulary Size
The assessment of individual language proficiency is often linked to the amount of vocabulary mastered. The greater the amount of vocabulary mastered, the higher the mastery of a person's language. One of the goals of the Primary School Standard Curriculum (KSSR) and the Secondary School Standard Curriculum (KSSM) in the context of Malaysian education is to increase students' vocabulary mastery.
The ability of an individual to have and master a significant amount of vocabulary is a key factor in determining an individual's level of language proficiency. Indeed, several previous studies suggest that an individual's ability to master a language is influenced by their command of vocabulary , and the success of vocabulary learning is seen as based on students' mastery of quantity and in-depth knowledge of vocabulary (Ngalawi & Zainal, 2020).
The concept of vocabulary size has been discussed in detail in previous studies. Vocabulary size is defined as the number or quantity of words mastered by a person. This understanding is supported by Nation (2001), who stated that vocabulary size refers to the number of words known by students at a level of mastery in a particular language. Nation (2001) also added that vocabulary size is considered a benchmark in determining the level of individual mastery in language skills. This view is supported by , who defined vocabulary size as the quantity and number of words mastered by an individual. The ability to master a large amount of vocabulary will make students more confident in their language learning (Curtis, 2006). Vocabulary size is a stock of basic words mastered by individual students to be used in various situations, known as the "lexicon" (Razak, 2018).
The discussion about vocabulary size has been widely done in previous studies, including through a study conducted by Husain and Mohamad (2020) that investigated the size of the Arabic language vocabulary of University Institute of Technology Mara (UiTM) students from two aspects, namely receptive and productive. The findings found that the size of the students' receptive vocabulary was below the desired level, which was 1885 words, while the size of the productive vocabulary showed 1655 words that had been mastered by the students. They suggest that students should emphasise high-frequency vocabulary so that it can be used more effectively.
Wahab et al (2021) carried out a study on vocabulary size and knowledge of Arabic collocations among Malaysian Higher Religious Certificate (STAM) students. The findings of their study, which used the interpretation value of the mean score level set by Nunnally and Bernstein (1994), found that the scores of the vocabulary size test and the Arabic collocation test were at high, medium, medium low, and low levels. They explained that out of the 4000 vocabulary words that were tested, 935 vocabulary words mastered by students were at a low level, 1426 vocabulary words mastered by students were at a medium-low level, and 2267 vocabulary words mastered by students were at a medium-high level. Findings show that there is an increase in the mastery of vocabulary quantity among students based on their respective levels. Razak (2018), who conducted a study among Institute of Higher Education students, stated that the mastery of a total vocabulary of around 2000 high-frequency words is the first step in learning a foreign language, while the next emphasis is necessary on the mastery of academic vocabulary.
In addition, many previous studies have examined the amount of vocabulary that students need to master in order to help them communicate, thus using the language well in everyday life. Richard and William (1993) asserted that secondary school students should learn between 2000 and 3000 new vocabulary words each year to master the subjects learned at the secondary level. According to Liu Na and Nation (1985), for tertiary level, such as university level, students should master 3000 basic words, depending on the field of study. This is different from the amount of vocabulary mastery required for learning the first language. For learning a first language, the average vocabulary mastery of students is around 12,000 to 20,000 words (Goulden et al., 1990). The significant difference in vocabulary mastery in first and second language learning is a factor of experience using the language on a daily basis since birth. Then, the vocabulary acquisition process is further strengthened through learning at the school level. In learning a second language, the amount that is considered suitable and relevant is around 3000 basic words, as in the syllabus of the Ministry of Education Malaysia . The next study conducted by Abdullah and Bakar (2022) on vocabulary mastery through the dimensions of Arabic vocabulary size and measurement in Malaysia found that the minimum level that students need to achieve, especially in Arabic vocabulary mastery, is 2000 words. This is based on the recommendations given by Nation (2001). Nevertheless, Nation also stated that in order to ensure that a student is fluent in language skills, their total vocabulary mastery should be in the range of 2000 to 5000 words.
The study of Zaini et al (2021) about the size of the Arabic vocabulary of final year students at the Selangor International Islamic University College found that the average vocabulary size mastered by the student participants was 2223 high-frequency words. The findings of their own previous research explained that the level of vocabulary mastery at a total of 2000 is enough to categorise students as being at the minimum level of language mastery. In addition, the statistical data obtained also show that the total word size mastered by Malay students is on average around 1231 words (Ngalawi & Zainal, 2020).  study is related to the construction of the Arabic vocabulary size level test, which involved a pilot study conducted to determine the vocabulary size level test method that is suitable for use and has psychometric characteristics of high reliability and validity. This study used word samples from Landau's vocabulary frequency list (1959), which were referenced using Abdul Rahman's vocabulary list (1994) for the suitability of Southeast Asian students. Then, screening was done from the perspective of learning through textbooks used at the school level. His research findings prove that the Arabic vocabulary size test he constructed and refined meets the psychometric criteria of reliability and validity. The high reliability value achieved through the implementation of the test proves that it can consistently measure the mastery of the student's vocabulary size.  (2017) Mastering the vocabulary is one of the learning goals that students should acquire in the context of Arabic education in Malaysia. Based on Table 1, the student's learning period starts from elementary level to secondary level, which takes almost 10 years. Therefore, students should have mastered a minimum of 3000 words throughout their learning at the primary and secondary levels .
Next, studies conducted by Husain and Mohamad (2020); Qi et al (2022) illustrate how the size of the vocabulary mastered by students can be determined by their level of mastery. Husain and Mohamad (2020) explained that determining the size of students' vocabulary can be carried out through two forms of testing. The first test involves testing receptive vocabulary, such as the Eurocentres Vocabulary Size Test (EVST), Vocabulary Level Test (VLT), and Vocabulary Knowledge Scale (VKS). The next test is the evaluation of productive vocabulary using the Expressive Vocabulary Test (EVT) and the Productive Vocabulary Test (PVLT). The use of the Vocabulary Level Test (VLT) is more synonymous with most researchers in determining the level of mastery of students' total vocabulary because it is easy to handle and easy to understand. Furthermore, it provides findings that have a good level of reliability. According to them, in-depth research needs to be given to the calculation aspect by emphasising the use of terms that have been determined by Beglar and Nation (2013); Goulden et al (1990); Nation (2001) in applying a scientific approach that involves measuring the quantity of vocabulary, including tokens, types, lemmas, and word families.

Vocabulary Depth
The level of linguistic knowledge known as vocabulary knowledge has a significant impact on the four language abilities of listening, speaking, reading, and writing. In terms of meaning, vocabulary knowledge refers to two components that are combined into one, namely the size component and the vocabulary depth component. The two components are used as a yardstick to test a person's level of mastery in learning Arabic. Schmitt (2014); Maskor and Baharudin (2020), in their studies, reported that most students find it difficult to guess the meaning of a single word and remember it for a long time because they do not understand the meaning of the word. In their study, it was also stated that the mastery of vocabulary knowledge is highly dependent on the approach used when learning vocabulary.
Word acquisition in vocabulary learning is limited. This is because most students are unable to make accurate inferences that are appropriate to the context of the word. Vocabulary mastery needs to refer to aspects of ideas, facts, thoughts, knowledge, and how information is presented accurately and clearly (Mezah & Mohammad, 2013). The view is supported by Milton (2009);O'Dell (2000), who stated that vocabulary knowledge is a continuum between the number of words mastered and knowledge of the meaning of words and how that knowledge is used in the right situation. Henriksen (1999) divided vocabulary knowledge into three levels that are necessary for vocabulary researchers to understand vocabulary knowledge in depth. He categorised vocabulary knowledge using dimensions. The first dimension is known as the partial knowledge to exact knowledge dimension. This dimension is closely related to the quantity, which is the size of the vocabulary. The second dimension is the dimension of the depth of vocabulary knowledge, which refers to the extent of a person's knowledge of various aspects of word knowledge. The next dimension is the ability to use vocabulary, from receptive to productive. This dimension is an advantage for a student if the student is able to use their understanding of vocabulary to be able to express the words in writing, speech, and so on.
Laufer and Goldstein's (2004) study shows that the depth of vocabulary is the knowledge of words. On the other hand, a group of researchers stated that vocabulary depth is a component of vocabulary knowledge that refers to the speaker's level of understanding of the word. Past scholars, such as Palmberg (1987), argued that vocabulary depth is a continuation of progressive levels of knowledge in vocabulary learning. While Qian (2002) explained that the depth of vocabulary refers to the student's knowledge of the meaning of words in depth, which includes pronunciation, spelling, meaning, frequency, morphology, syntax, and collocation according to the appropriate context. Haastrup and Henriksen (2000) stated in their study that knowledge of meaning and collocation are the aspects highlighted in vocabulary depth. Webb (2013) defined vocabulary depth as in-depth knowledge of one word when communicating and writing, which includes aspects of syntax, frequency of use, concept and meaning, appropriateness, and so on. This is supported by Schmitt (2014), who explained the depth of vocabulary as components of vocabulary knowledge, lexical organisation, receptive and productive mastery, and fluency. In addition to that, Rizan and Baharudin's (2021) study regarding the level of students' vocabulary knowledge found that the level of Arabic vocabulary knowledge of their study participants was at a moderately high level. The sample of participants in their study was a total of 214 people, involving four government-aided religious schools (SABK) in Selangor.

Methodology
The design of this study uses a quantitative approach that focuses on a survey-type study. The quantitative approach was chosen because it can explain a phenomenon in the form of numbers and measurements. In this study, the study population involved a total of 2653 Form Four Arabic students at secondary religious schools ( This study uses proportional stratified random sampling to determine the selection of participants. Stratified random sampling, or proportional strata, was used in this study due to the fact that the population breakdown for each sub-group is not the same. The number of population fractions between sub-groups should be balanced so that sampling error can be reduced, the sample is better, and there is a large potential statistical effect (Konting, 2005). Therefore, the selection of this sampling method was used to ensure that the number of samples for each of the nine districts in Selangor involved was balanced.
The percentage of the number of samples for each of the nine districts in Selangor involved was obtained by dividing the number of samples in each district by the total population. Then, the sample size for each district was determined by multiplying the percentage of the sample by the desired number of samples. The sample size used in this study, which was 335 people, meets the formula and table for determining the sample size as proposed by (Krejcie and Morgan, 1970). The researcher chose the Krejcie and Morgan formula because it uses the confidence level in the sample size calculation. Table 2 demonstrates the number of Form Four Arabic-language students in secondary religious schools in Selangor and the percentage in detail. This research instrument is in the form of a test to test the level of mastery of Arabic vocabulary among students in the fourth grade of secondary religious schools in Selangor. This test is built in the form of dichotomous questions, which are two-choice answers (right or wrong) and multiple-choice responses to test receptive vocabulary. The vocabulary depth test focuses on the construction of denotative meaning, semantic relationships, word formation, and word combinations, which are measured using multiple choice responses and filling in the blanks. This test is adapted from Maskor's (2020) study, which is the Arabic Vocabulary Knowledge Test (PekkA), which was developed to measure secondary school students' Arabic vocabulary proficiency.
Vocabulary mastery test questions have a total of 37 items. The first 20 questions involve the aspect of vocabulary size, which includes elements of nouns (9 items), verbs (6 items), and pseudowords (5 items), and determining the answer dichotomously "true or false." The rest of the questions, which are 17 items, test the depth aspects that include elements of denotative meaning (8 items), semantic relationships (4 items), word formation (6 items), and word combinations (2 items). The findings of the study show that the vocabulary mastery test is one of the areas of study that has rarely received attention from past researchers (Hashim, 2020). This instrument had been tested for its content validity using a three-panel assessment and its reliability, which resulted in a Cronbach's alpha coefficient value of 0.83. Before collecting data for the actual study, this instrument was tested in a pilot study done at a religious secondary school (Arab) in Selangor, involving 34 participants.

Findings and Discussion
Referring to Table 3, the findings of the descriptive analysis show that the mastery of the size of the students' Arabic vocabulary was high (mean = 15.26, SD = 2.748). For the level of mastery of the depth of knowledge of Arabic vocabulary, the students were at a moderate level (mean = 7.16, SD = 2.687). Overall, the findings show that the overall score percentage of the Arabic vocabulary mastery test conducted was at a moderate level (mean = 59.21, SD = 11.98). The score percentage portrays the actual level of mastery of Arabic vocabulary among secondary religious school students in Selangor.  Figure 1 shows the frequency of percentage marks or the overall score of the Arabic vocabulary proficiency test of Form Four students of secondary religious schools in Selangor through a bar chart. Table 4 summarises the findings of the percentage of the overall score of the Arabic students' vocabulary mastery test.  Table 4, it can be concluded that a total of 37 students had a good command of Arabic vocabulary, representing 11.04%. A total of 224 students, representing a percentage of 66.87%, obtained a medium-level test score. Meanwhile, a total of 74 students, representing 22.09%, showed a weak level of mastery of Arabic vocabulary. The findings based on the score percentage in Table 3.16 explain that the level of Arabic vocabulary mastery of the students was generally at a moderate level (mean = 59.21, SD = 11.98).

Figure 1 Frequency of Percentage Marks/Overall Score of the Arabic Vocabulary Mastery Test of Form Four Students of Secondary Religious Schools in Selangor
The findings suggest that the students' level of mastery of Arabic vocabulary was at a moderate level. This explains that students know the meaning of at least half or almost threequarters of the words they should know. This situation will make the language learning space for students wider to master because they have a good mastery of Arabic vocabulary. This statement is supported by Jaafar et al. (2019), who claimed that good vocabulary mastery opens up a wider space for students to master the next level in learning Arabic, which is grammar. The moderate vocabulary mastery finding is in line with some previous studies (Maskor, 2020;Kamarudin et al., 2017), which also found that the participants' Arabic vocabulary mastery was in a moderate state. However, the findings of this study were found to be inconsistent with the findings of a study conducted on tahfiz students by Jaafar et al. (2019). Their study shows that the level of Arabic vocabulary mastery among tahfiz students was high. This is likely because tahfiz students are often faced with the task of memorising the text of the Quran and often understand the meaning of words and verses before memorising the Quran (Hilmi et al., 2021). According to Entwistle and Entwistle (2003), memorization and understanding will produce better-quality effects. The findings of this descriptive analysis explain that the students' level of mastery of Arabic vocabulary was at a moderate level where there were differences in two aspects that were measured, namely the aspect of size and the aspect of depth of Arabic vocabulary. The size aspect showed a high level, while the depth aspect showed a medium level.
Next, Figure 2 details the frequency of correct answer scores achieved through 20 words in the Arabic vocabulary size mastery test assessed on students. A student who successfully obtains 1 mark means that the student is interpreted as having a total vocabulary of 100 words.

Mean
=15.26 Standard Deviation =2.748 Level =High Looking at Figure 2, the highest frequency is a total of 64 students, representing a percentage of 19.1% who answered correctly for the 16 questions asked. By definition, the average student has mastered a total vocabulary of 1600 words. Only a total of nine students, representing a percentage of 2.69%, were interpreted to have a total vocabulary of 2000 words. This diagram also shows that most students managed to answer correctly in the range between 11 and 19. The overall mean value for the aspect of Arabic vocabulary size showed a high level (mean = 15.26, SD = 2.748). Therefore, it can be said that the mastery of the size of the Arabic vocabulary among Form Four students of religious secondary schools in Selangor was at a good level.
The mastery of the Arabic vocabulary size aspect by the students in this study showed a good level. This explains that SAM students master and know the meaning of three-quarters of the total number of words they should master. Form Four students of religious secondary schools in Selangor had a mastery of vocabulary in the range of 600 to 2000 words. This amount of vocabulary is enough to categorise students as being at the minimum level of language proficiency for junior high school students (Abdullah & Bakar, 2022;Zaini et al., 2021).
The findings of this finding are in line with the study of Ngalawi and Zainal (2020), who stated that the statistical data obtained showed that the average number of words mastered by Malay students was around 1231 words. This finding is also consistent with the finding of Husain and Mohamad's (2020) study, which was conducted on tertiary students, where the size of the Arabic receptive vocabulary of students was below the desired level, with 1885 receptive words and 1655 mastered productive words.
The effect of mastering a sufficient vocabulary size leads to an increase in students' selfconfidence in learning the language, especially Arabic. This matter has been discussed by Curtis (2006), who underlines that students will feel confident learning a language if they master the amount of vocabulary they have on a large scale. This is because the size of the vocabulary becomes a benchmark for an individual to assess the level of language mastery he or she possesses (Nation, 2001).
A sufficient number of words mastered by the students will help them express their ideas and views in writing. This point is confirmed by Jasni and Zainal (2020), where they emphasise that the effect of solid vocabulary mastery will help students to write effectively, even though the statistics of previous studies have found that the writing skills of secondary religious school students were at a weak level. This happens as a result of students' lack of mastery over the aspect of vocabulary size (Baharudin & Ismail, 2016). Figure 3 details the frequency of correct answer scores achieved by all participants through the 17 question items found in the vocabulary depth mastery test. The findings show that none of the students managed to correctly answer all the tested question items. The highest frequency shows a total of 53 students, representing 15.82%, answering the five questions correctly. Based on the findings, it can also be observed that most students managed to answer the questions correctly only in the 4-9 range. The highest total score for the depth test is 15 correct, which involves the frequency of one student representing 0.3%. 14 questions were answered correctly, involving 4 students, representing 1.19%. Only one student managed to get all the questions correct, representing 0.3%; two students answered correctly on two questions out of the 17 questions tested, representing 0.6%. Overall, the level of mastery of the depth of Arabic vocabulary among religious secondary school students in Selangor was at a moderate level (mean = 7.16, SD = 2.687).

Figure 3 Frequency of Correct Answer Scores in the Vocabulary Depth Mastery Test
The findings of this study show that the depth of Arabic vocabulary among SAM students was satisfactory. The aspect of vocabulary depth refers to the extent of the student's knowledge of the mastered words. The difficulty for students to master a good number of words is caused by their weakness to understand the meaning of the words they learn. This matter is explained in a study conducted by Maskor and Baharudin (2020); Schmitt (2014), who emphasised that students should study the meaning of a word to make it easier for them to remember the word. This statement is also agreed upon by Milton (2009);O'Dell et al (2000), who argued that vocabulary knowledge is a continuation of the number of words mastered with knowledge of the meaning of words and how students use those words in accordance with the situation.
For the vocabulary depth aspect as well, the findings obtained are the same as the findings of the study by (Ridha et al., 2022). Their study shows that the level of students' knowledge of vocabulary was at a moderate level. This shows that the students' knowledge of the meaning of the mastered vocabulary was equal. Students managed to master every statement of the tested items well, even though the words tested were rarely encountered by them. In addition, the findings of the study in this section are seen to be contrary to the findings of some past studies (Kamaruddin & Baharudin, 2017;Rizan & Baharudin, 2021), which show the level of students' vocabulary knowledge at a moderately high level. Students at the medium and medium-high levels are classified as students who are able to read and understand the structure of Arabic sentences well and make fewer obvious mistakes. This is because previous research findings confirm that most students use dictionaries and guess the meaning of words as their approach to language learning (Citrayasa et al., 2022). Furthermore, students are aware that the limited space of the language environment does not guarantee that they will be able to maximise their language use and vocabulary knowledge in real-life situations (Sadat, 2017).

Conclusion
This study was carried out to identify the mastery of Arabic vocabulary from the aspects of size and depth among Form Four religious secondary school (SAM) students in Selangor. This study demonstrates that vocabulary mastery among Selangor SAM students was at a moderate level. The mastery of size was found to be at a high level, which means that the students had a sufficient size of Arabic vocabulary, while the depth of Arabic vocabulary was at a medium level. This study also reveals information on students' Arabic vocabulary mastery, which was found to be able to be improved by controlling several variable factors such as learning motivation, vocabulary learning strategies, learning environment, and so on. This study clearly proves the validity of the instrument used, which was based on a careful development procedure that includes aspects of size and depth following the Common European Test of Reference for Language (CEFR) concept. This study is seen as being able to make a significant contribution to the importance of shaping students' autonomy when helping them develop their vocabulary learning abilities. Further studies are suggested to focus on improving the depth of Arabic vocabulary and the ability to assess aspects of Arabic vocabulary through quality instruments.