Why don't you answer to thank you?

Answer 1

"Thanks" is the interjection form of "Thank you," a proper spoken form of "I thank you." * The proper reply to "thank you" is "you are welcome", which has been shortened in common English to "you're welcome" or the familiar but improper "you welcome". Example : John :"Thanks!"

Bill : "You're welcome." * A newer colloquial use is "np" or "no problem" as an answer for "thank you" :

Example:

Bill : "Here's a cookie."

John :"Thanks!"

Bill : "No problem."