Covivant is a neologism coined about 20 years ago to replace the phrase "living in sin". A covivant is the person you are living with but not technically married to.

Say it with me:

"Hakuna Matata!" err I mean "Covivant!"

Vivant comes from the French word for "to live" and the co comes from ... well.. comes from like you know co... cohabitate, cosign, post coital, codependency.

It seems preferable to uptight middle-America straights who see "life partner" as a term only employed in the lesbian community. Others view "common law husband/wife" as screaming "trailer park".