(of a word or expression) not agreeing with grammatical principles
"The teacher marked his essay because he used an incorrect verb form that violated basic grammar rules."
Not correct; erroneous or wrong.
"The student's answer was incorrect because he forgot to add the final zero in his calculation."
In plain English: Incorrect means something is wrong, false, or not right according to what should be true.
"The teacher marked my answer incorrect because I had forgotten to add units."
The word incorrect entered English from Middle French as a single term rather than being formed by combining the prefix in- with correct. It has retained its original meaning of not being right or accurate since arriving in the language.