major form class

form class, part of speech, word class - one of the traditional categories of words intended to reflect their functions in a grammatical context

noun - the word class that can serve as the subject or object of a verb, the object of a preposition, or in apposition

verb - the word class that serves as the predicate of a sentence

adjective - the word class that qualifies nouns

adverb - the word class that qualifies verbs or clauses