[Howlin]

because adultery is having sex with any person out of wedlock.

Main Entry: adul·tery
Pronunciation: &-'d&l-t(&-)rE
Function: noun
Inflected Form(s): plural -ter·ies
Etymology: Middle English, alteration of avoutrie, from Middle French, from Latin adulterium, from adulter adulterer, back-formation from adulterare
: voluntary sexual intercourse between a married man and someone other than his wife or between a married woman and someone other than her husband; also : an act of adultery

[wagglebee]

Upon further research, I was incorrect. The sin that is committed IS NOT adultery, it is FORNICATION.

Fornication: The free act of carnal intercourse between persons who are not married but who are free to marry. Fornication is always gravely wrong because it deprives sexual intercourse of the order which the good of the human race demands. It is a substantial inversion of an essential order.
http://www.catholic-forum.com/saints/ncd03343.htm