“What’s the definition of Christianity?”
Have you ever been asked that question? If not, how would you answer it? How about beginning with letting God answer the question:
For I passed on to you as of first importance what I also received—that Christ died for our sins according to the scriptures, and that he was buried, and that he was raised on the third day according to the scriptures. – 1 Corinthians 15:3-4
If you declare with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved. – Romans 10:9-10
No doubt, you could offer a number of comments – including testimony of what Christ has done in your own life – to help a person understand what this worldview called Christianity is.
But the Bible is a wise place to begin.
Sola Scriptura, Nick