There are those who think that a Christian is someone who lives a good life, goes to a church and practises the religious rituals. Others think that it is being born into a Christian family, while others think that they are crusaders who force everyone to embrace their religion. 
None of these definitions are true, even though some may hold passionately to them. The best source for a definition of a Christian is the Bible itself. In Acts 11 we read that the disciples of Jesus in Antioch of Syria were first called Christians. It certainly was not a term of respect then. It was a label to put the disciples down and ostracise them. And there are many Christians in many nations today who experience the same thing, even to the point of being martyred for their faith in Jesus Christ.
The Bible says that a Christian is one who has received the Lord Jesus Christ, has believed in His name, and, as a result, has been given the authority to become a child of God, John 1:12. That necessitates being born again, as Jesus told the Jewish teacher, Nicodemus, in John 3. That is how a Christian becomes a child of God. The act of receiving the Lord Jesus Christ, and accepting everything that He did in His death on the cross and rising again to life, initiates a miracle in the person’s life. Immediately the Holy Spirit comes into his/her spirit and gives life to the spirit which was dead in sin, as the Bible says. It’s an instantaneous birth! What a miracle! 
But another miracle takes place as well. Before becoming a Christian, a person is living in the kingdom of darkness, which is ruled by the Devil, or Satan. By nature, this kingdom keeps people ignorant of the state and their final destiny, because they can’t see while they are in the dark. But when a person receives the Lord Jesus Christ, and is born again, a radical transformation happens, and a real transference takes place from one kingdom to another. The Bible says in Colossians 1:13 that God has rescued us from the power of darkness and transferred us into the kingdom of His Son, the kingdom of light. Actually it is a change of spiritual citizenship. That is an incredible change! All of a sudden we can see where we really have been and how different things look in the kingdom of light. An amazing change of perspective takes place after God has rescued the person. 
To be a Christian is really to be a disciple of Jesus. When Jesus talked with His disciples for the last time while He was here on Earth, He delegated His authority to them to go and make disciples of all nations—not just to start a new world-wide religion. 
So what does it mean to be a disciple? Again, the Bible gives us the best definition. Jesus said this to those who heard and believed in Him, “You are truly My disciples if you keep obeying My teachings. And you will know the truth, and the truth will set you free.” John 8:31-32, NLT. 
A disciple is like an apprentice, who not only learns the trade, but also catches the spirit of the master craftsman. He or she is a learner, one who follows both the teacher and the teaching. Since we have received Jesus Christ as our Saviour and Lord, He is our Teacher and we are His disciples. That is what the first Christians in the New Testament were called, disciples of Jesus Christ. 
So in the Growing Deep and Strong Series we call new Christians “disciples”, because it indicates that the new Christian is following the Master, Jesus. We want the disciples to receive His teaching, read and study the Bible for themselves, and follow Him in their everyday lives. That’s where the radical change can really be seen.
 

David W Searle, co-author of Growing Deep and Strong