I haven't seen (someone) in years

Talk about seeing someone for the first time in a long time with the phrase "I haven't seen ___ in ___":

I haven't seen you in over a year!

You use "in years" when you can't remember how long it's been since you saw them, but you know it was more than one or two years.

You can use this phrase when talking to anyone - it's not especially casual or formal.

This phrase appears in these lessons: