bad temper vs spleen

bad temper and spleen both are nouns.

Word	Noun	Adjective	Verb	Adverb
bad temper	Yes	No	No	No
spleen	Yes	No	No	No

As nouns, spleen is a hyponym of bad temper; that is, spleen is a word with a more specific, narrower meaning than bad temper:

Other hyponyms of bad temper include irascibility, quick temper, short temper, conniption, fit, scene, tantrum.

bad temper (noun)	spleen (noun)
a persisting angry mood	a large dark-red oval organ on the left side of the body between the stomach and the diaphragm; produces cells involved in immune responses
	a feeling of resentful anger