Certain
Certain adjective - Having or showing a mind free from doubt.
Usage example: I'm certain that they'll arrive on time
Unsure
Unsure adjective - Not feeling sure about the truth, wisdom, or trustworthiness of someone or something.
Usage example: unsure of her ability to handle the pressure of competing in the Olympic Games
Both words in one sentence
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Early on, he's unsure whether he really deserves it or because of a certain nepotism, since he's also the current president's adoptive son.
Source: Film / The Omen (2006) -
If he's unsure how viewers will react to a certain game, he'll also ask if he should continue it.
Source: Lets Play / JackSepticEye -
Unreliable Narrator: It's unsure whether this is a full on Continuity Reboot or if Graham is embellishing on certain facts and stories.
Source: Video Game / King's Quest (2015)
Cite this Source
Unsure and Certain. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/certain/unsure
Certain & Unsure. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/certain/unsure>.
Unsure or Certain. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/certain/unsure.
Google Ngram Viewer shows how "certain" and "unsure" have occurred on timeline