bad luck vs sewer

bad luck and sewer both are nouns.

Word	Noun	Adjective	Verb	Adverb
bad luck	Yes	No	No	No
sewer	Yes	No	No	No

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

Other hyponyms of bad luck include weakness, adversity, hard knocks, hardship, gutter, toilet, hard cheese.

bad luck (noun)	sewer (noun)
unnecessary and unforeseen trouble resulting from an unfortunate event	a waste pipe that carries away sewage or surface water
an unpredictable outcome that is unfortunate	misfortune resulting in lost effort or money
an unfortunate state resulting from unfavorable outcomes	someone who sews