This book is concerned with the investigation of the lexicon of the English language. It covers topics such as the historical development of the lexicon, social stratification, encoding in specialized lexicons, stylistic peculiarities of the lexemes, complexity of lexical meaning, multi-word lexemes, etc. The book is intended to introduce students of EFL to the study of words and lexicon by presenting the major achievements and concepts of Lexicology and related linguistic fields. Furthermore, it is also designed as a workbook in Lexicology to help students gain a good working knowledge of the lexical resources available in the English language. In each section, theoretical is-sues are covered to give the students the foundation to proceed with the Exercises assigned in the English vocabulary. The theoretical material is de-signed to give insight into the basic theory of lexically-oriented language studies. We have devised the Exercises in each section to assist students’ advances in analysing and understanding the structure, content and lexical relations in the English lexicon.