posture vs slouch

posture and slouch both are nouns.

Word	Noun	Adjective	Verb	Adverb
posture	Yes	No	Yes	No
slouch	Yes	No	Yes	No

As nouns, slouch is a hyponym of posture; that is, slouch is a word with a more specific, narrower meaning than posture:

Other hyponyms of posture include manner of walking, walk, gracefulness, awkwardness, clumsiness.

posture (noun)	slouch (noun)
the arrangement of the body and its limbs	a stooping carriage in standing and walking
characteristic way of bearing one's body	an incompetent person; usually used in negative constructions
capability in terms of personnel and materiel that affect the capacity to fight a war
a rationalized mental attitude

posture (verb)	slouch (verb)
assume a posture as for artistic purposes	walk slovenly
behave affectedly or unnaturally in order to impress others	assume a drooping posture or carriage