The Malay Archipelago vs Malayan

The Malay Archipelago and Malayan both are nouns.

Word	Noun	Adjective	Verb	Adverb
The Malay Archipelago	Yes	No	No	No
Malayan	Yes	Yes	No	No

The Malay Archipelago (noun)	Malayan (noun)
a group of islands in the Indian and Pacific Oceans between Asia and Australia	a member of a people inhabiting the northern Malay Peninsula and Malaysia and parts of the western Malay Archipelago

The Malay Archipelago (adjective)	Malayan (adjective)
	of or relating to or characteristic of the people or language of Malaysia and the northern Malay Peninsula and parts of the western Malay Archipelago
	of or relating to or characteristic of Malaysia