Nice to meet you.

Say this when you meet someone for the first time:

Nice to meet you.

For a little more formality, you can add "It's":

It's nice nice to meet you.

If you've met someone before and you see them again, don't say "Nice to meet you" again; they might think that you don't remember them. In that case, say:

Nice to see you.

This phrase appears in these lessons: