Which term would be associated with the expression of a thought or idea style?

The term that best fits the expression of a thought or idea style is phraseology. Phraseology refers to the particular choice and arrangement of words or phrases used in communication. It encompasses the unique way in which ideas are articulated and can reflect individual style, familiarity with certain expressions, and specific contexts in which language is used.

For instance, different writers or speakers may prefer certain phrases or structures that distinguish their style, contributing to their voice and tone. Phraseology captures these nuances more effectively than the other options.

Syntax pertains to the arrangement of words within sentences and focuses specifically on the rules governing sentence structure. While it is essential for clarity and grammaticality, it does not encompass the broader idea of expressive style.

Grammar encompasses the entire system of rules governing language — including syntax, morphology, and punctuation — but does not specifically highlight the individual style of expressing thoughts or ideas.

Dialect refers to a particular form of language that is specific to a region or social group. While it can influence style in terms of word choice and pronunciation, it does not specifically address the manner in which one expresses thoughts and ideas on a more personalized level.

Thus, phraseology is the term most closely aligned with the concept of the expression style of thoughts or ideas.