Functional
Functional adjective - Being in effective operation.
Key and functional are semantically related. In some cases you can use "Key" instead an adjective "Functional".
Key
Key adjective - Coming before all others in importance.
Functional and key are semantically related. Sometimes you can use "Functional" instead an adjective "Key".
Both words in one sentence
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She continues to insist that she's Not A Lesbian with an exception for Zii, but it's obvious to anyone who knows what the words mean that she's a functional bisexual — with Zii as her closet key.
Source: Webcomic / Ménage à 3 -
While the Arch to Earth is no longer functional, they hope that one of the new "arrivals" will act as a key to activate the portal.
Source: Earth That Was -
The actual product crashed regularly, lacked key documentation, generated non-functional code, and even had unremoved warnings that it was not for public release.
Source: Obvious Beta
Cite this Source
Key and Functional. (2016). Retrieved 2026, August 03, from https://thesaurus.plus/related/functional/key
Functional & Key. N.p., 2016. Web. 03 Aug. 2026. <https://thesaurus.plus/related/functional/key>.
Key or Functional. 2016. Accessed August 03, 2026. https://thesaurus.plus/related/functional/key.
Google Ngram Viewer shows how "functional" and "key" have occurred on timeline