According to the dictionary, fornication means ‘sexual intercourse between a man and woman not married to each other.’
The Bible says, “But fornication and all uncleanness or covetousness, let it not even be named among you, as is fitting for saints.” Ephesians 5:3 NKJV
In other words, God does not approve of a lifestyle of living together and having sex without being married.
Jesus said to the woman He met at the well, “You don’t have a husband— for you have had five husbands, and you aren’t even married to the man you’re living with now.” John 4:17-18 NLT
Jesus was making it obvious to this woman what He thought about her lifestyle of living in the sin of fornication!