What type of morpheme is added to a word without altering its grammatical function?

The correct response is that an inflectional morpheme is added to a word without altering its grammatical function. Inflectional morphemes modify a word to express different grammatical categories such as tense, mood, aspect, number, or case, but do so without changing the word's part of speech. For example, adding "-s" to "cat" to form "cats" changes the number but not the fundamental role of "cat" as a noun.

Derivational morphemes, on the other hand, can change the grammatical category or meaning of a word. For instance, adding "-ness" to "happy" creates the noun "happiness," transforming the adjective into a noun. Similarly, root morphemes are the base words that derive meaning, and compound morphemes consist of two or more independent words combined to create a new meaning.