What are the parts of words that have meaning, such as roots and affixes, called?

The parts of words that carry meaning, including roots and affixes, are known as morphemes. A morpheme is the smallest grammatical unit in a language that holds meaning; it can be a standalone word (like "book") or a component of a word (like the prefix "un-" in "unhappy"). Understanding morphemes is essential as they help in constructing words and figuring out their meanings, which is crucial for vocabulary development and language acquisition, especially in a sheltered English immersion environment where meaning-making is a priority.

Phonemes refer to the smallest units of sound in a language and do not relate directly to meaning. Syntax deals with the structure and rules that govern the arrangement of words in sentences, while discourse pertains to connected speech or writing beyond the level of a sentence. Thus, morphemes specifically focus on meaning within language components, making this the correct choice in the context of the question.