Japanese vs ninja

Japanese and ninja both are nouns.

Word	Noun	Adjective	Verb	Adverb
Japanese	Yes	Yes	No	No
ninja	Yes	No	No	No

Japanese (noun)	ninja (noun)
the language (usually considered to be Altaic) spoken by the Japanese	a class of 14th century Japanese who were trained in martial arts and were hired for espionage and assassinations
a native or inhabitant of Japan	a member of the ninja who were trained in martial arts and hired for espionage or sabotage or assassinations; a person skilled in ninjutsu

Japanese (adjective)	ninja (adjective)
of or relating to or characteristic of Japan or its people or their culture or language