grammar: (noun) the study of the structure of language, word order, and how words change (according to tense, for example); the system of rules that guides the use of language; a book about grammar
grammer: (noun) a term for someone who uses Instagram (who may or may not care about grammar)
Grammar can also be an adjective when it is used to describe something else. For example: grammar class, grammar mistake, grammar lover (that’s me).
I have seen “grammar” spelled as “grammer” many, many times. I always considered it a spelling mistake that wasn’t really confusing. It was truly a case of “you know what I meant, right?” Then I took a class with someone who referred to people who use Instagram as grammers. As it turns out, I am a grammar grammer.