[Grammar] reply TO you, or reply you?

[Gerundle]

My friend said "reply TO you" is correct, and not "I will reply you." Why????
Please explain in grammatical terms

 

[Barb_D]

In grammatical terms, 'reply' does not take a direct object. It's not a transitive verb. So you don't "reply a person."

In contrast, 'answer' can be transitive and take an object. I will answer the phone, I will answer the question, I will answer you after I've had a chance to think about it for a bit.