In contrast to function words, content words, or lexical words (including nouns, verbs, adjectives, and most adverbs), are words that carry the content or the meaning of a sentence. They are open-class words. Open classes accept the addition of new morphemes (words), through such processes as compounding, derivation, inflection, coining, and borrowing.
John, room, answer
happy, new, large, gray
search, grow, hold, have
really, completely, very, also,