Hi,
I encourage you to register.
The correct way to spell the word is
grammar.
There are two types of grammar teachers:
prescriptive and
descriptive. The grammar books you're used to are what linguists call prescriptive, in the way they prescribe rules for proper usage. For several hundred years, "grammar" was synonymous with "prescriptive grammar." You went to a book to get the official word: thou shalt not
split infinitives, thou shalt not
end sentences with prepositions. (This is presumably why you're reading this guide now: to find out what's "right" and what's "wrong.")
Linguists today are justly dubious about such things, and most spend their time on descriptive grammars: descriptions of how people really speak and write, instead of rules on how they should.
Prescriptive versus Descriptive Grammars