monotheism vs Islam

monotheism and Islam both are nouns.

Word	Noun	Adjective	Verb	Adverb
monotheism	Yes	No	No	No
Islam	Yes	No	No	No

As nouns, Islam is a hyponym of monotheism; that is, Islam is a word with a more specific, narrower meaning than monotheism:

monotheism: belief in a single God
Islam: the monotheistic religious system of Muslims founded in Arabia in the 7th century and based on the teachings of Muhammad as laid down in the Koran

Other hyponyms of monotheism include Judaism, Islamism, Mohammedanism, Muhammadanism, Muslimism.

monotheism (noun)	Islam (noun)
belief in a single God	the monotheistic religious system of Muslims founded in Arabia in the 7th century and based on the teachings of Muhammad as laid down in the Koran
	the civilization of Muslims collectively which is governed by the Muslim religion