private detective vs shamus

private detective and shamus both are nouns.

Word	Noun	Adjective	Verb	Adverb
private detective	Yes	No	No	No
shamus	Yes	No	No	No

As nouns, private detective and shamus are synonyms defined as:

private detective and shamus: someone who can be employed as a detective to collect information and assist in criminal investigations

Other synonyms of private detective include operative, PI, private eye, private investigator, sherlock.

private detective (noun)	shamus (noun)
someone who can be employed as a detective to collect information and assist in criminal investigations	someone who can be employed as a detective to collect information and assist in criminal investigations