Ninigi vs Ninigi-no-Mikoto

Ninigi and Ninigi-no-Mikoto both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ninigi	Yes	No	No	No
Ninigi-no-Mikoto	Yes	No	No	No

As nouns, Ninigi and Ninigi-no-Mikoto are synonyms defined as:

Ninigi and Ninigi-no-Mikoto: grandson of Amaterasu and first ruler of Japan

Other synonyms of Ninigi include Ninigino-Mikoto.

Ninigi (noun)	Ninigi-no-Mikoto (noun)
grandson of Amaterasu and first ruler of Japan	grandson of Amaterasu and first ruler of Japan