Second language acquisition depends crucially on the amount of vocabulary one possesses as vocabulary forms the biggest part of the meaning of any language. Vocabulary, however, is the biggest problem for most learners and vocabulary acquisition used to be a neglected aspect of language learning. Although a lot of studies have been conducted in recent years about vocabulary learning strategies used by native language learners, little attention has been given to foreign learners of English. Moreover, most of the studies done so far focus on general language learning strategies. Not enough attention has been paid to vocabulary learning strategies. This book, therefore, tries to investigate effective factors in learners’ vocabulary acquisition such as vocabulary learning strategies, vocabulary size and reading comprehension. It tries to shed light on interrelationship among these variables and suggests the best strategies and methods to learn vocabulary and should be especially useful for curriculum designers, publishers, learners of English, teachers, lecturers, or anyone else who may be engaged in the process of teaching and learning English.