词汇学（lexicology）是以语言的词汇为研究对象，研究词汇的起源和发展、词的构造、构成及规范，词汇学分为：

• 历史词汇学，主要研究词汇的起源和发展，也从属于历史语言学；
• 描写词汇学，主要研究某个时期的词汇系统，也从属于共时语言学；
• 普通词汇学， 研究语言词汇的一般理论，其中包括比较语言学的研究方法。

从广义讲，词汇学还包括词源学、语义学和词典学。

Lexicology is the part of linguistics which studies words. This may include their nature and function as symbols, their meaning, the relationship of their meaning to epistemology in general, and the rules of their composition from smaller elements (morphemes such as the English -ed marker for past or un- for negation; and phonemes as basic sound units). Lexicology also involves relations between words, which may involve semantics (for example, love vs. affection), derivation (for example, fathom vs. unfathomably), usage and sociolinguistic distinctions (for example, flesh vs. meat), and any other issues involved in analyzing the whole lexicon of a language.