Third person singular present tense: turns aside from a course, rule, or standard; departs from what is expected.
From Latin deviare, combining de- (away) + via (way/road). The verb entered English in the 16th century from scientific and philosophical texts.
The word deviate is fascinating because it literally means to leave the road—Roman roads were straight engineered structures, so any deviation from them was noticeable. That literal image stuck with us metaphorically for centuries.
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