What is the primary distinction between derivational and inflectional morphemes?

The primary distinction between derivational and inflectional morphemes lies in their functions in language. Inflectional morphemes serve a grammatical purpose and modify a word to express different grammatical categories, such as tense, mood, number, or case, without creating a new word. For instance, the addition of "-s" to "cat" to form "cats" indicates pluralization but does not change the fundamental meaning of the word.

In contrast, derivational morphemes are concerned with the creation of new words and often alter the meaning or part of speech of the base word significantly. For example, adding the prefix "un-" to the adjective "happy" creates "unhappy," which changes the meaning entirely.

The correct response highlights that inflectional morphemes maintain the original word's identity and do not generate new lexical items, thereby clarifying their distinct role in linguistic structure compared to derivational morphemes.