Brain
Brain noun - The part of a person that feels, thinks, perceives, wills, and especially reasons.
Usage example: I'd love to get inside his brain and experience the world as he experiences it
Reason is a synonym for brain in intelligence topic. In some cases you can use "Reason" instead a noun "Brain", when it comes to topics like wisdom.
Reason
Reason noun - The ability to learn and understand or to deal with problems.
Usage example: you'll need to use all of your reason to get out of this tight spot
Brain is a synonym for reason in wisdom topic. Sometimes you can use "Brain" instead a noun "Reason", if it concerns topics such as intelligence, mental analysis.
Mutual synonyms
How words are described
Both words in one sentence
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Since she takes control of the brain to do so, this Magical Girl is able to speak and reason using the host's intelligence.
Source: Manga / Magical Girl Apocalypse - And the only reason I'm not even tryin' to change your mind on it is that anything approaching rational thought would bounce off that thick plate on your forehead—assuming that's Klingon ridges and not a massive brain tumor responsible for your long string of bad decisions.
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In the The Grim Adventures of Billy & Mandy episode "Brown Evil" Mandy reveals the reason why she sent Billy outside to deal with the zombies is because he has no brain.
Source: Who Even Needs a Brain?
Cite this Source
Reason and Brain. (2016). Retrieved 2026, August 14, from https://thesaurus.plus/related/brain/reason
Brain & Reason. N.p., 2016. Web. 14 Aug. 2026. <https://thesaurus.plus/related/brain/reason>.
Reason or Brain. 2016. Accessed August 14, 2026. https://thesaurus.plus/related/brain/reason.
Google Ngram Viewer shows how "brain" and "reason" have occurred on timeline