learning a second or foreign language requires the manipulation of four main skills, namely, listening, reading, speaking, and writing which lead to effective communication. it is obvious that vocabulary is an indispensible part of any communication, so without a vocabulary, no meaningful communication can take place and meaningful communication relies heavily on vocabulary. one fundamental factor is the amount of vocabulary an individual possesses. therefore, vocabulary forms the meaningful part of any language (mccarthy, 1988; as cited in hamzah, kafipour, & kumar abdullah, 2009). vocabulary is the group of words that a person or a group of people knows how to use. your vocabulary is all the words you know and use regularly. vocabulary is a group or stock of words used in a particular way by a certain group of people regarding their language. it is important and it is vital to communicate with others and understand what one is reading. it is obvious that information, which is known as a language-based activity, is fundamentally and profoundly dependent on vocabulary knowledge. learners must have access to the meanings of words that teachers, their surrogates, other adults, books or films use to guide them into contemplating known concepts in novel ways in order to learn something new. second language (l2) acquisition depends crucially on the development of a strong vocabulary. in second language acquisition (sla), a sub-discipline known as second language vocabulary acquisition (slva), researchers have focused their attention on the need for second language learners to optimize their vocabulary knowledge (singleton, 1999; schmitt, 2000). over the years, estimates of student vocabulary size have varied greatly, hindered in part by issues such as the types of vocabularies being considered (e.g., receptive/ productive or oral/print). it is evident that vocabulary is indispensable for successful communication in any language. the question is addressed which specific part of the target lexicon should be presented to language learners at what stage and it is followed by a short summary of how word knowledge has been defined in the sla literature. consequently, the focus of attention changed from acquisition to vocabulary assessment. the familiarity of learners with learning strategies has been emphasized as a facilitating factor in the process of language learning. besides, as regards second or foreign language learning, many researchers have been done in order to deal with language learning strategies (lls).these researches had a feasible goal, was the identification of the ways of enhancing the language learner to become more self-directed, resourceful, effective, and flexible in their learning. consequently, the invaluable importance of learning strategies has been emphasized as a rudimentary factor in order to overcome the difficulties of l2 learning (omalley & chamott, 1990; weinstein et al, 2000; hall, 2000). moreover, the acquisition of vocabulary has been emphasized in the second language pedagogy and research. consequently, the neglected concept of vocabulary has been shifted to the position of some significance. as well as the familiarity of language learning skills, the development of vocabulary knowledge has been emphasized as a fundamental factor in order to deal with all learning processes. learners are encountered with various vocabularies in different texts, so the fear of unknown vocabulary has threatened learners as big hindrance in the process of l2 learning. the appropriate meaning of a word in a given context can be regarded as a dimension of vocabulary knowledge, so its increase raises the vocabulary size of the learner. based on the ideas discussed above, it is crucial to be aware of how learners adopt the strategies effectively with vocabulary size. thus, the principal focus of present study is to examine which language learning strategies are effective for the learners’ use and how the usefulness of vocabulary size is linked in order to help teachers to design lesson plan and to construct feasible instructions so that effectively support learners’ competence in english language. 3. method participants the present study was conducted at zoha english language center. a total of 150 efl learners, 47 males and 143 females, within the age range of 15 - 32 participated in the study. all participants were from interchange intro level up to toefl level. these learners were considered as consistent learners of the center. they were involved in an english language program at zoha center during the fall 2011 semester. table 1 characteristics of the participants number of the participants 150 age range 15-32 general english proficiency level elementary, intermediate, advanced sex females& males instrument an already determined standard placement test of oxford university and cambridge university (2001, version 1) was used to divide the participants into elementary, intermediate, and advance proficiency levels. this instrument included 60 multiple-choice question, cloze comprehension passage, vocabulary, and grammar sections. another instrument, which was applied in the present study, was the strategy inventory learning (sill, version 7).besides, some background information questions about the learners’ age, gender, name, and proficiency levels were included. the sill was used to ascertain the frequency of students’ uses of language learning strategies. regarding the content validity of the inventory, oxford and burry- stock (1995) state that the content validity of the instrument was determined by professional judgment and it is found to be very high. although the version sill 7 includes 50 questions and 6 subscales, in the present study due to some infeasibilities ‘only 35 questions and 3 subscales as metacognitive (items 15-23), cognitive(items 1-14), and social/ affective strategies(items 24-35) were included. the following numbers indicates how often the learner uses the strategies. never or almost never true of me = 1 generally not true of me = 2 somewhat true of me = 3 generally true of me = 4 always or almost always true of me = 5 the participants were required to write their answers on a separate answer sheet. having all the answers completed, the values assigned to each item in each section were added. then, they were divided into the number of items in each part. the same procedures were repeated for each section and values ranging between 1 to 5 were obtained. these values demonstrate the profile of a learner. that is, the strategies used by learners and their frequency. due to the high accessibility of sill which was achieved in previous studies such as bobko (2001), and litwin’s (1995) cronbach alpha was .82, so the reliability of the test is acceptable .thus, the test is a reliable instrument to estimate students’ english language strategies. another study was done by other researchers who, proved the accessibility of the sill test by using internal consistency reliability of the sill as .94 based on a 505-person sample (yang, 2010) and .92 based on a 315-person sample (watanabe, 1990). content validity is .99 based on independent raters (oxford &burry-stock, 1995). the second tool, which was used in the present study was schmitts vocabulary learning strategy questionnaire adopted from bennet (2006) with a reliability coefficient of 0.78. another study was done by ozdamar (2002), who used cronbach alpha. according to his findings, the reliability of each item was high (alpha=0.8851). the sill has been translated into several languages such as persian, japanese, spanish, turkish, and chinese. therefore, in the present study, the translated version of sill was used for elementary level learners. in the present study, the vocabulary level test was used to find out the size of vocabulary items. the test was designed by norbert schmitt (2008, version 2). schmitt (2001) wrote three new forms of the test following the original specification by taking fresh samples of words for each level. its utility has been proved for diagnostic vocabulary teaching and has been widely used and validated by different researchers (laufer &nation, 1995; laufer and nation 1999; laufer, 1998; lufer and paribakht, 1998). meara (1996) calles it the nearest thing we have to standard test in vocabulary. vocabulary size testing has been found to be a useful tool in diagnostic or placement exams. it can discriminate between groups of learners (meara, 1996) and aid in admissions (laufer, 2003), as well as help in placing students into appropriate institutional placement levels within a program (laufer & nation, 1999). the format of the test involves word definition matching exercise. although, this test is regarded as a standard practice, it is the words that test takers need to match to the definitions provided. that is, definitions rather than words comprise the test items. this unconventional format was designed in order to involve as little reading as possible while at the same time minimizing chances of guessing correctly (read , 2001). each frequency level of the test consisted of six words and three definitions. testees were required to match target words with their corresponding definitions as demonstrated below: 1 business …..6…part of a house 2 clock …..3…animal with four legs 3 horse ….4…. something used for writing 4 pencil 5 shoe 6 wall as indicated above, there were 3 words to be selected by the students. test-takers need, however, to know 6 words because they should check every word against the definitions in order to make correct matches.