What type of suffix creates a new word derived from a base word?

The correct answer is derivational suffix. This type of suffix serves to create a new word that has a different meaning or function from the base word to which it is attached. For example, adding the suffix "-ness" to the adjective "happy" results in the noun "happiness," fundamentally transforming the word's role in a sentence and its meaning.

Derivational suffixes are particularly important in vocabulary development as they allow for greater expression and complexity in language by forming various parts of speech—nouns, verbs, adjectives, and adverbs—from a single root. This process enriches the language and enhances understanding.

In contrast, inflectional suffixes modify a word's tense, number, or case without creating a new word. They adjust the form of the word to fit grammatical rules but do not change its base meaning or create a new lexical item. Exclamatory suffix and conjunctional suffix are not standard categories in English morphology; therefore, they do not apply in this context.