hard line vs posture

hard line and posture both are nouns.

Word	Noun	Adjective	Verb	Adverb
hard line	Yes	No	No	No
posture	Yes	No	Yes	No

As nouns, posture is a hypernym of hard line; that is, posture is a word with a broader meaning than hard line:

Other hypernyms of hard line include position, stance.

hard line (noun)	posture (noun)
a firm and uncompromising stance or position	the arrangement of the body and its limbs
	characteristic way of bearing one's body
	capability in terms of personnel and materiel that affect the capacity to fight a war
	a rationalized mental attitude

hard line (verb)	posture (verb)
	assume a posture as for artistic purposes
	behave affectedly or unnaturally in order to impress others