What morphological process involves changing a word to enhance its meaning without changing its category?

Affixation is the morphological process that involves adding prefixes, suffixes, or infixes to a base word to enhance or modify its meaning while keeping the word within the same grammatical category. For example, by adding the prefix "un-" to "happy," the new word "unhappy" retains its status as an adjective, but its meaning is altered to indicate the opposite state.

The other processes listed involve different mechanisms. Diminution refers to a process where a word is changed to convey a smaller or lesser form, often resulting in a different connotation or context. Inflection involves modifying a word to express grammatical relationships, such as tense, number, or case, which can lead to changes in grammatical category in some instances. Dissociation refers to a form of word alteration where a word's meaning or usage diverges significantly from its original form or function, which typically does not involve just enhancing the meaning while remaining in the same category.