tough luck vs hardship

tough luck and hardship both are nouns.

Word	Noun	Adjective	Verb	Adverb
tough luck	Yes	No	No	No
hardship	Yes	No	No	No

As nouns, hardship is a hyponym of tough luck; that is, hardship is a word with a more specific, narrower meaning than tough luck:

Other hyponyms of tough luck include weakness, adversity, hard knocks, gutter, sewer, toilet, hard cheese.

tough luck (noun)	hardship (noun)
an unfortunate state resulting from unfavorable outcomes	something hard to endure
	something that causes or entails suffering
	a state of misfortune or affliction