Christian (noun)
a person who claims or acknowledges to being a follower of Jesus Christ and / or Christianity
Usage examples:
It is easier to become a Christian than to live as one.
More people claim to be Christians on surveys than attend Church.
Plural - Christians
Christian (adjective)
Usage examples:
True Christian behaviour is characterised by love.
His Christian beliefs seemed strange to many of the natives.
The Christian religion has several sects with many denominations.
Christianity (Proper Noun / Name)
Name of a major religion based on the life of Jesus Christ and particularly the interpretation given thereto by Paul of Tarsus.
Usage examples:
The central text of Christianity is The Holy Bible.
Christianity has many adherents.
See Christianity for further clarification and information.
Synonyms - The following words can be used as synonyms in particular contexts,
Christian church, Christian faith, Christian religion