luck vs ill luck

luck and ill luck both are nouns.

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

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

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

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