I was just wondering: I think that if someone sleeps with a married person but they are not married, they now to are committing adultery? And if that person, who was not married, sleeps with someone else later in life, who is not married, does that new person commit adultery too? Just wondering how it works because I know they are committing fornication, but what about adultery since they are both not married?
Adultery is having sex where one of the people involved is married, but not to each other. Fornication is a broader word for having sex with someone to whom you are not married. Thus, fornication can include adultery. Both fornication and adultery are sins (Hebrews 13:4).
If an unmarried person has sex with a married person, then they are committing adultery. If the unmarried person has sex with an unmarried person, then they are committing fornication. It doesn't matter what they had done in the past. Sins are described in terms of what law is being violated at the time.
See Sex for detailed definitions and scripture references.