Der Junge ist rothaarig is grammatically correct.
The sentence (not sentance) is grammatically correct
No, not usually, because normally it is grammatically incorrect.
Before is a preposition, so it's grammatically incorrect to use it as the last word in a sentence.
Yes, it is.
They were so engaged with each others thinking that they exchanged email addresses after the conference.
The sentence (not sentance) is grammatically correct
That sentence is grammatically correct.
Grammatically incorrect.
No, not usually, because normally it is grammatically incorrect.
The sentence is grammatically correct.
Yes. Although the word order is unusual, and not suited for normal speech, it is not grammatically incorrect.
No, the sentence "You wake at 9 am" is grammatically incorrect. It should be written as "You wake up at 9 am."
A mathematically and grammatically incorrect sentence.
The second sentence is grammatically incorrect. The correct sentence should be: I want to visit Hawaii.
the sentence given is incorrect. Dad has brought presents for you and for her.
Never isn't a verb, so a sentence with it as a verb would be grammatically incorrect.
A sentence with broken grammar is often referred to as a "grammatically incorrect" or "ungrammatical" sentence.