Grammatically

The sentence is not grammatically accurate.

This sentence is grammatically correct.

Strictly speaking, this sentence is grammatically incorrect.

A sentence can state something false while at the same time be grammatically correct.

The sentence "This sentence is grammatically correct." is grammatically correct.

Grammatically there is nothing wrong with this sentence, but I think it would never actually be used.

Though grammatically there is nothing wrong with this sentence, I doubt if anyone would actually ever use it.

Your English is grammatically correct, but sometimes what you say just doesn't sound like what a native speaker would say.

Choose the grammatically incorrect sentence.

This sentence seems to be grammatically correct.

For example, once the child is able to parse (i.e. grammatically analyse) an adult utterance such as Help Daddy and knows that it contains a verb phrase comprising the head verb help and its complement Daddy, then (on the assumption that the language faculty specifies that all heads of a given type behave uniformly with regard to whether they are positioned before or after their complements), the child will automatically know that all verbs in English are canonically (i.e. normally) positioned before their complements.