Algerian capital vs Algiers

Algerian capital and Algiers both are nouns.

Word	Noun	Adjective	Verb	Adverb
Algerian capital	Yes	No	No	No
Algiers	Yes	No	No	No

As nouns, Algerian capital and Algiers are synonyms defined as:

Algerian capital and Algiers: an ancient port on the Mediterranean; the capital and largest city of Algeria

Algerian capital (noun)	Algiers (noun)
an ancient port on the Mediterranean; the capital and largest city of Algeria	an ancient port on the Mediterranean; the capital and largest city of Algeria