Which term describes the process of changing word forms to express different grammatical relations?

The term that describes the process of changing word forms to express different grammatical relations is inflection. Inflection involves modifying a word to convey different tense, mood, voice, aspect, person, number, gender, and case. For example, in English, a verb might be inflected to indicate past tense, as in "walk" becoming "walked." Similarly, nouns can change form to indicate pluralization, such as "cat" becoming "cats."

This process is essential for conveying the correct meaning in sentences, as it helps indicate relationships between words and clarify subject-verb agreement. Inflection is a common feature in many languages, playing a crucial role in grammar and syntax.

In contrast, derivation refers to the process of creating a new word by adding prefixes or suffixes, which often change the word's meaning or part of speech but do not focus on grammatical relations. Phonology pertains to the sound system of a language rather than word forms. Synthesis, in a linguistic context, usually refers to combining elements rather than modifying them to express grammatical relations.