Doubtful
Doubtful adjective - Not feeling sure about the truth, wisdom, or trustworthiness of someone or something.
Usage example: he was doubtful about the decision to complete the project despite its mounting problems
Sure
Sure adjective - Having or showing a mind free from doubt.
Usage example: are you absolutely sure that she said she was coming today?
Doubtful is an antonym for sure in topics: certain, unsure, inevitable, self-confident, physically stable.
Nearby Word: surely
Both words in one sentence
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No one's sure what exactly is in the Sepulchre, but given that it can Mind Rape entire crew of an aforementioned miles-long flying cathedral from hundreds of thousands of kilometers away, it's doubtful anyone wants to know.
Source: Cool Starship - Sure, he leads and supports Link on his quest to defeat Majora and save Termina, but given how unclear his motives are, and how shady and downright nightmarish he is, his status as Big Good becomes kind of doubtful.
Source: Mysterious Backer
Cite this Source
Sure and Doubtful. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/doubtful/sure
Doubtful & Sure. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/doubtful/sure>.
Sure or Doubtful. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/doubtful/sure.
Google Ngram Viewer shows how "doubtful" and "sure" have occurred on timeline