Nippon vs Nihon

Nippon and Nihon both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nippon	Yes	No	No	No
Nihon	Yes	No	No	No

As nouns, Nippon and Nihon are synonyms defined as:

Nippon and Nihon: a constitutional monarchy occupying the Japanese Archipelago; a world leader in electronics and automobile manufacture and ship building

Other synonyms of Nippon include Japan.

Nippon (noun)	Nihon (noun)
a constitutional monarchy occupying the Japanese Archipelago; a world leader in electronics and automobile manufacture and ship building	a constitutional monarchy occupying the Japanese Archipelago; a world leader in electronics and automobile manufacture and ship building