You haven't chat with me for a long time .Please don't forget me .Oh,you are my best friend.friend要为单数还是复数啊?

You haven't chat with me for a long time .Please don't forget me .Oh,you are my best friend.
friend要为单数还是复数啊?

单数,Friend与you一起

单数

单数,如果这句话是you are one of my best friends,这时候friend要变为friends