The Ten Most Common Ways Unmarried People Introduce Their Partners (in order of frequency):*
1. partner (also life partner, unmarried partner, domestic partner)
2. boyfriend/girlfriend
3. significant other or S.O.
4. the person's name without a descriptive word
5. friend
6. husband/wife
7. roommate or housemate
8. lover
9. spouse
10. sweetie or sweetheart

* according to interviews conducted by Marshall Miller and Dorian Solot for Unmarried to Each Other: The Essential Guide to Living Together as an Unmarried Partner, in 2001. To read the full list of over forty words unmarried people use to introduce their partners, check out Unmarried to Each Other.

Do you have a different or new word to suggest?  Tell us about it!  For example, some people are trying out "para-kin."