Islam is the religion of the Muslims, which was started by Mohammed.
2. uncountable noun
Some people use Islam to refer to all the countries where Islam is the main religion.
...relations between Islam and the West.
Islam in British English
(ˈɪzlɑːm)
noun
1.
the religion of Muslims, having the Koran as its sacred scripture and teaching that there is only one God and that Mohammed is his prophet; Mohammedanism
2.
a.
Muslims collectively and their civilization
b.
the countries where the Muslim religion is predominant
Derived forms
Islamic (Isˈlamic)
adjective
Word origin
C19: from Arabic: surrender (to God), from aslama to surrender