judo vs martial art

judo and martial art both are nouns.

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

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

judo: a sport adapted from jujitsu (using principles of not resisting) and similar to wrestling; developed in Japan
martial art: any of several Oriental arts of weaponless self-defense; usually practiced as a sport

Other hypernyms of judo include athletics, sport.

judo (noun)	martial art (noun)
a sport adapted from jujitsu (using principles of not resisting) and similar to wrestling; developed in Japan	any of several Oriental arts of weaponless self-defense; usually practiced as a sport