Let us consider a few Bible examples of how the word is used. "I tell you, Nay: but, except you repent, ye shall all likewise perish." (Lk.13:3). Repent or perish. Kinda strong and definite language. The seriousness of this warning is found two verses farther, verse 5, where the exact warning is repeated. There it is, repent or perish, no ifs, ands or buts about it. 

Another familiar passage where except appears is John 3:5: "Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God." The importance of the word except is in the importance of seeing the kingdom of God. This is the only place in the gospels where Jesus speaking to Nicodemus is found. However, in the epistles the importance of the new birth is clearly emphasized. 

How important is the kingdom of God? Paul says the kingdom is to be delivered up to God the Father, (1 Cor.15:24). How important is this? Jesus said, "No man cometh unto the father, but by me." (Jn.14:6b). Jesus also said, "But seek ye first the kingdom of God, and his righteousness..." (Matt. 6:33). If the kingdom is to be sought first does this not indicate its importance? But what about the emphasis placed on a new birth according to the epistles? 

In his letter to Christians at Rome Paul reminds them of how they had entered into a newness of life (Rom.6:3-4). This happened at baptism. To the church of God at Corinth Paul mentioned this birth more than once (1Cor.4:15; 2 Cor.5:17);(See Acts 18:8). In his letter to Titus Paul describes the new birth thusly: "Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost." (Titus 3:5). Peter also refers to the new birth in 1 Peter 1:23. 

How important is the word except? It is as importance as repentance and as the new birth.