You know you are a language nerd when…

[sulayman]

…you check out the ”Customers Who Bought This Item Also Bought” section of a language guide book’s page and

realize that you own almost every single book in those 10+ pages.

[lovemwaf]

you giggle to yourself when you are chatting in your native tongue when someone says a word that has a completely different meaning in another language

[jcannon]

...you wake up from a really scary dream and swear in a language that isn't your own!

[Trellum]

You know a lot interesting facts about a lot different languages, incluiding the ones that are almost extinct or dying   

[gegegeno]

You listen to people talking near you on the bus to try and work out what language they're speaking...

PS: @sulayman, I didn't even think that made me a language nerd until you pointed it out. I've read every language book in my Amazon recommendations!