Part of Speech (definition)
'Part of speech' (also syntactic category, lexical category, lexical class) is the category of a word indicating the function of it, usually syntactic. Common examples of 'parts of speech' include nouns, verbs, adjectives, prepositions, and adverbs.
"Syntax: A Generative Introduction" (2007 Second Edition) by Andrew Carnie
"Introduction to Typology: The Unity and Diversity of Language" (1999) by Lindsay J. Whaley