Key
Key adjective - Coming before all others in importance.
True
True adjective - Being exactly as appears or as claimed.
Both words in one sentence
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One of the key facts of his villain mythology is that only one person has ever seen his true face and lived to tell the tale, setting up a Chekhov's Gun regarding his true appearance.
Source: The Un-Reveal - Parodied in "Happy Sad Songs and Sad Happy Songs" which, true to form, changes the key of various songs.
Source: The Cover Changes the Meaning -
Learning this is also true of the campaign's Big Bad is the key to ending the campaign non-violently.
Source: Everyone Is Gay
Cite this Source
True and Key. (2016). Retrieved 2026, July 29, from https://thesaurus.plus/related/key/true
Key & True. N.p., 2016. Web. 29 Jul. 2026. <https://thesaurus.plus/related/key/true>.
True or Key. 2016. Accessed July 29, 2026. https://thesaurus.plus/related/key/true.
Google Ngram Viewer shows how "key" and "true" have occurred on timeline