Though friendships differ endless in degree ,
The sorts , methinks, may be reduced to three.
Ac quaintance many, and Con quaintance few;
But for In quaintance I know only two--
The friend I've mourned with, and the maid I woo!

Samuel Taylor Coleridge

http://www.poemhunter.com/poem/the-three-sorts-of-friends-fragment/