How to say "Boyfriend" in Chinese:

Nan2 peng2 you5

What are these numbers? 

Nan2 = boy
peng2 you5 = friend

In Chinese, the word boyfriend is formed just as it is in English - by taking the word for boy and the word for friend and putting them together.

Here are a few good combinations to commit to memory:

My boyfriend = Wo3 de4 nan2 peng2 you5
Your boyfriend = Ni3 de4 nan2 peng2 you5
His boyfriend = Ta1 de4 nan2 peng2 you5