California Teacher Credentialing Examination (CSET) Practice Test

A derivational morpheme is indeed a meaningful unit that can change the part of speech of a word. For example, adding the suffix “-ly” to the adjective "quick" transforms it into the adverb "quickly." This ability to alter the grammatical category demonstrates how derivational morphemes contribute to vocabulary development and the complexity of language.

The other options miss key aspects of derivational morphemes. While a unit that does not change part of speech would describe inflectional morphemes instead, elements that have no meaning do not constitute morphemes at all, and phonemes are the smallest units of sound that do not convey meaning.