area vs realm

area and realm both are nouns.

Word	Noun	Adjective	Verb	Adverb
area	Yes	No	No	No
realm	Yes	No	No	No

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

area (noun)	realm (noun)
a part of a structure having some specific characteristic or function	a knowledge domain that you are interested in or are communicating about
the extent of a 2-dimensional surface enclosed within a boundary	the domain ruled by a king or queen
a part of an animal that has a special function or is supplied by a given artery or nerve	a domain in which something is dominant
a subject of study
a particular geographical region of indefinite boundary (usually serving some special purpose or distinguished by its people or culture or geography)
a particular environment or walk of life