“Fornication” (porneuo) is often used as a noun in the New Testament, but in 1 Cor. 10:8 is a present tense verb. Although it is a verb, it still describes all types of sexual sin. For other places where fornication occurs as a noun see 6:18, and these references in the book of Revelation: 2:14, 20; 17:2; 18:3, 9. Whether used as a noun or a verb, fornication describes departures from God’s “religious norms (e.g. homosexuality, promiscuity, pedophilia, and especially prostitution” (Colin Brown, 1:497).