is it grammaticly correct to use words such as "gonna" and "wanna" in a sentence?
for example:i'm gonna send you an e-mail as soon as possible.
i know that those words are used in slang language ,but today you can see them even in academic text.
I agree. In fact, I find them quite irritating to see in writing, althougth they don't bother me at all in spoken English. But languages do change. Maybe one day they will be correct. Latin turned to French through many such orally-inspried changes, e.g. "au jour de hoc die" At the light of this day, becoming aujourd'hui, today. Maybe old geezers were ever thus: against change.