In the Bible, sexual immorality is a term used to describe sexual acts that violate social conventions and are outside of God's design for enjoying sexual pleasure. The Greek word porneia is often translated as "sexual immorality" in the New Testament and can also be translated as "whoredom" or "fornication". It's used to describe any sexual expression that takes place outside of a biblically defined marriage relationship, such as premarital sex, sex with prostitutes, or sex with a wife who is menstruating or pregnant. The Bible also considers it sexual immorality to have sex on a Sabbath or for the sole purpose of fulfilling lust, rather than to make babies.