copper's nark vs informer

copper's nark and informer both are nouns.

Word	Noun	Adjective	Verb	Adverb
copper's nark	Yes	No	No	No
informer	Yes	No	No	No

As nouns, informer is a hypernym of copper's nark; that is, informer is a word with a broader meaning than copper's nark:

copper's nark: an informer or spy working for the police
informer: one who reveals confidential information to the police or other authority

Other hypernyms of copper's nark include betrayer, blabber, rat, squealer.

copper's nark (noun)	informer (noun)
an informer or spy working for the police	one who reveals confidential information to the police or other authority