tough luck vs luck

tough luck and luck both are nouns.

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

As nouns, luck is a hypernym of tough luck; that is, luck is a word with a broader meaning than tough luck:

tough luck: an unfortunate state resulting from unfavorable outcomes
luck: your overall circumstances or condition in life (including everything that happens to you)

Other hypernyms of tough luck include circumstances, destiny, fate, fortune, lot, portion.

tough luck (noun)	luck (noun)
an unfortunate state resulting from unfavorable outcomes	an unknown and unpredictable phenomenon that causes an event to result one way rather than another
	an unknown and unpredictable phenomenon that leads to a favorable outcome
	your overall circumstances or condition in life (including everything that happens to you)