nightlife vs amusement

nightlife and amusement both are nouns.

Word	Noun	Adjective	Verb	Adverb
nightlife	Yes	No	No	No
amusement	Yes	No	No	No

As nouns, amusement is a hypernym of nightlife; that is, amusement is a word with a broader meaning than nightlife:

nightlife: the entertainment available to people seeking nighttime diversion
amusement: an activity that is diverting and that holds the attention

Other hypernyms of nightlife include entertainment.

nightlife (noun)	amusement (noun)
the activity of people seeking nighttime diversion (as at the theater, a nightclub, etc.)	an activity that is diverting and that holds the attention
the entertainment available to people seeking nighttime diversion	a feeling of delight at being entertained