Christendom (noun)

1. The community of Christian believers throughout the world.
2. The territory or countries where Christianity is the dominant religion.
3. The collective body of Christian institutions, culture and civilization.

Origin:

Derived from the words "christ" and "dom" meaning domain, or the realm of the followers of christ.

Examples:

1. The Pope is the spiritual leader of Christendom.
2. Christendom was once divided by the East-West Schism.
3. The crusades were fought to reclaim the Holy Land for Christendom.
4. The medieval Christendom was shaped by the Catholic Church.
5. Christendom has faced a decline in the number of followers in recent years.