"
- "and from fornication; not spiritual fornication or idolatry, but fornication taken in a literal sense, for the carnal copulation of one single person with another" (Gill's commentary
, Acts 15:20, emphasis added)
- "Fornication - Hebrew: zanah / Greek: porneia
Fornication is voluntary sexual intercourse between a man and woman who are not married to each other. Adultery is one type of fornication.
In every form, fornication was sternly condemned by the Mosaic law among God's people, the Israelites (Lev. 21:9; 19:29; Deut. 22:20-11, 23-29; 23:18; Ex. 22:16). (See ADULTERY.)
Fornication is also mentioned many times in the New Testament (Matt. 5:32; 19:9; John 8:41; Acts 15:20, 29; 21:25; Rom. 1:29; 1 Cor 5:1, 6:13, 18, 7:2; 10:8; 2 Cor 12:21; Gal 5:19; Eph 5:3; Col 3:5; 1 Thess. 4:3; Jude 1:7; Rev. 2:14, 20-21; 9:21; 14:8; 17:2,4).
"The Greek word for 'fornication' (porneia) could include any sexual sin committed after the betrothal contract. ...In Biblical usage, 'fornication' can mean any sexual congress outside monogamous marriage. It thus includes not only premarital sex, but also adultery, homosexual acts, incest, remarriage after un-Biblical divorce, and sexual acts with animals, all of which are explicitly forbidden in the law as given through Moses (Leviticus 20:10-21). Christ expanded the prohibition against adultery to include even sexual lusting (Matthew 5:28)." (Dr. Henry M. Morris)
The word "fornication" is sometimes used in a symbolic sense in the Bible, for example, meaning a forsaking of God or a following after idols (Isa. 1:2; Jer. 2:20; Ezek. 16; Hos. 1:2; 2:1-5; Jer. 3:8-9)." (christiananswers.net
, emphasis added)
So the Greek word
porneia can mean adultery (which is sex outside of marriage), incest (which is sex outside of marriage), prostitution (which is sex outside of marriage), fornication (which is sex outside of marriage), etc., depending on the context.
What it boils down to is that sex outside of marriage is always a sin, whether it's adultery, incest, prostitution, fornication, etc.