Definitions for "Part of speech"
the grammatical classification of a word: noun, adjective, preposition, etc.
noun, pronoun, verb, preposition, adjective, adverb, participle, gerund, gerundive, expletive, interjection, conjunction, etc.
the class of units used in the description of a language, e.g. noun, verb, noun phrase, verb phrase.
Keywords:  classes, set
a set of classes