Which literary technique involves altering a word to form a different part of speech?

Derivation is the correct answer because it refers to the process of forming a new word by adding prefixes or suffixes, or by changing the base form of a word to create a different part of speech. For example, the word "happy" can be transformed into "happiness," which is a noun, or "unhappy," which involves adding a prefix. This technique allows for the expansion of vocabulary and nuanced expression in language.

Grammar refers to the set of rules governing the structure of sentences and the relationships between words, rather than the process of altering words themselves. A suffix is a specific type of affix added to the end of a word that can also change its form, but it is a component of the derivation process rather than a broader technique. Transformation generally describes a change in form, appearance, or structure but does not specifically relate to the alteration of words to create different parts of speech.