Shia vs Shiah Islam

Shia and Shiah Islam both are nouns.

Word	Noun	Adjective	Verb	Adverb
Shia	Yes	No	No	No
Shiah Islam	Yes	No	No	No

As nouns, Shia and Shiah Islam are synonyms defined as:

Shia and Shiah Islam: one of the two main branches of orthodox Islam; mainly in Iran

Other synonyms of Shia include Shiah.

Shia (noun)	Shiah Islam (noun)
one of the two main branches of orthodox Islam; mainly in Iran	one of the two main branches of orthodox Islam; mainly in Iran