aikido vs martial art

aikido and martial art both are nouns.

Word	Noun	Adjective	Verb	Adverb
aikido	Yes	No	No	No
martial art	Yes	No	No	No

As nouns, martial art is a hypernym of aikido; that is, martial art is a word with a broader meaning than aikido:

aikido: a Japanese martial art employing principles similar to judo
martial art: any of several Oriental arts of weaponless self-defense; usually practiced as a sport

aikido (noun)	martial art (noun)
a Japanese martial art employing principles similar to judo	any of several Oriental arts of weaponless self-defense; usually practiced as a sport