premarital sex, n.Definitions

Premarital sex is not pre-marital if you don't get married.

Premarital sex is tantamount to eating supper before saying grace

Premarital sex is not premarital sex if you have no intention of getting married.

Premarital sex is now compulsory test of future physical compatibility. However, results can be inconclusive, and the test may need repeating for many years before a couple finally recognise they are incompatible, and the man marries someone younger.