The Greek noun porneia (πορνεία) broadly denotes sexual immorality, fornication, prostitution, or unlawful sexual intercourse. It appears about 26 times in the NT. Jesus identified it as the one permissible ground for divorce (Matthew 5:32; 19:9).
Porneia is one of the NT's primary ethical battlegrounds. Paul lists it first among works of the flesh (Galatians 5:19) and commands believers to 'put to death' everything belonging to their 'earthly nature: sexual immorality (porneia), impurity, lust, evil desires' (Colossians 3:5). The reason is theological: believers' bodies are 'temples of the Holy Spirit' (1 Corinthians 6:19), and sexual sin defiles that temple. The Jerusalem Council's ruling (Acts 15:20, 29) included abstaining from porneia as one of the non-negotiables for Gentile believers. In Revelation, porneia becomes a symbol of spiritual apostasy — the great Babylon is 'the mother of prostitutes' (pornon), representing idolatry and unfaithfulness to God. Sexual holiness is covenant faithfulness made visible in the body.