What is the study of word structure in linguistics known as?

The study of word structure in linguistics is referred to as morphology. Morphology deals specifically with the internal structure of words and how they are formed from morphemes, which are the smallest grammatical units in a language. This includes understanding how affixes (prefixes and suffixes) combine with root words to create new meanings or grammatical forms.

In contrast, syntax relates to how words are arranged to form sentences, phonology focuses on the sounds of speech and their systematic organization, and semantics concerns the meaning of words and sentences. Each of these fields addresses different layers of language, but morphology is uniquely centered on the composition and structure of individual words.