1. A religion based on the life and teachings of Jesus. Most forms of Christianity hold that Jesus is the son of God and is the second person of the Trinity, through whom humans may attain redemption from sin.

2. Christians as a group; Christendom.

3. The state or fact of being a Christian.

4. pl. Chris·ti·an·i·ties A particular form or sect of the Christian religion: the Christianities of antiquity.