Flat
Fixed
Fixed adjective - Having been established and usually not subject to change.
Usage example: the baseball card dealer's prices were fixed, so bargaining was not an option
Flat is a synonym for fixed in manner topic. You can use "Flat" instead an adjective "Fixed", if it concerns topics such as change.
Cite this Source
Fixed and Flat. (2016). Retrieved 2026, August 15, from https://thesaurus.plus/related/flat/fixed
Flat & Fixed. N.p., 2016. Web. 15 Aug. 2026. <https://thesaurus.plus/related/flat/fixed>.
Fixed or Flat. 2016. Accessed August 15, 2026. https://thesaurus.plus/related/flat/fixed.
Google Ngram Viewer shows how "flat" and "fixed" have occurred on timeline