**Fornication** *has* changed its meaning since 1611, so reading its definition in a modern English dictionary does little good. In 1611, fornication meant prostitution (as abundantly proven ad infinitum on the "goldenrule" website) and was a perfect translation of "porneia", which is the activity of "porné", prostitutes. Though the entry at dictionary.com on fornication is misleading, if you look up "fornicate", it will tell you what it meant about the time the KJV was written: http://dictionary.reference.com/browse/fornicate which was prostitution. Young's Literal translation renders it "whoredom".

God wrote his list of rules for sex, telling us what types of sex were sinful, i.e. "sexual immorality". The most convenient list is in Leviticus 18. You will find no requirement of marriage before sex or condemnation of premarital sex by God in that passage or any other passage. Such teaching is from the tradition of the church, not from scripture. 

The references to porneia in I Corinthians 6 is about temple prostitutes, brothels that operated for the good of the city and fully accepted by the populace of Corinth. The reference to "fornications" (plural) in 1 Cor.7:2 is also to these same brothels. **If you read 1 Corinth. 10:8, you will see that Paul uses porneia to refer to cult or "sacred" prostitution, joining to an idol by means of sex with a devoted prostitute.** This fits in perfectly with 1 Corinth. 6 esp. when he talks about this being the only sin that a believer can commit "against his own body" It is unique among all sex sins. There is no sin as harmful as this. Obviously, Paul is not talking about premarital sex here. He's saying that when a man has sex with a temple prostitute, he joins himself to that idol; that union invites demonic entrance into his body thus driving out the indwelling Spirit from His temple; this "takes away a member of the body of Christ" and is indeed a uniquely destructive sin. 

  Another reason that people have misunderstood 1 Cor. 7:2 is the failure to translate "have one's wife or husband" accurately. It means to have sex or be in a sexual relationship with someone. It doesn't mean "get a wife, so you won't have sex before marriage." Paul was saying "let every man have sex with his own woman, not with a temple prostitute." Several  commentaries bring out these points: 

http://www.enduringword.com/commentaries/4607  
http://tinyurl.com/GordonFeeCommentary   
http://www.biblestudytools.com/commentaries/gills-exposition-of-the-bible/1-corinthians-7-2.html 

Only a couple of translations have made the meaning clear for us, the NetBible being an example. Here is their note on this: 
>"Grk “each man should have his own wife.” “Have” in this context means “have marital relations with” (see the following verse). The verb ἐχέτω (ecetw, “have”) occurs twice in the Greek text, but has not been repeated in the translation for stylistic reasons. This verb occurs 8 times in the LXX (Exod 2:1; Deut 28:30; 2 Chr 11:21; 1 Esd 9:12, 18; Tob 3:8; Isa 13:16; 54:1) with the meaning “have sexual relations with,” and 9 times elsewhere in the NT with the same meaning (Matt 20:23; 22:28; Mark 6:18; 12:33; Luke 20:28; John 4:18 [twice]; 1 Cor 5:1; 7:29)."

Richard suggests that Strong's dictionary defines porneia as "all forms of sexual acts that are not within the confines of marriage" when in fact it doesn't say that at all. **RE: Deuteronomy 22:14**, when a man paid a bridal price for a girl, she was considered his wife from that day forward; it might be over a year later before they had the marriage feast and he took her as his bride. If this betrothed girl, his legal wife, had sex before her wedding day, she was guilty of a type of adultery and suffered the consequences. Comparing that situation to Exodus 22:16-17 sex with an unbetrothed virgin, the Bible clearly teaches that premarital sex is NOT a sin;  there was no punishment upon either of them. The man was forced to pay her bridal price for otherwise her family could never recover the lost money; the marriage was obligatory upon the man if the parents approved it.  

These passages only talk about virgin girls under their father's care and say NOTHIING about premarital sex by adult single females or males. There is no passage that speaks against males, whether single or married, having sex with an unattached female. Adultery laws only applied to sex with married women, not unmarried. 

I hope people will stop adding their own rules to the Bible; they're like the Pharisees who made the word of God of no effect by their traditions.