pickpocket vs thief

pickpocket and thief both are nouns.

Word	Noun	Adjective	Verb	Adverb
pickpocket	Yes	No	No	No
thief	Yes	No	No	No

As nouns, thief is a hypernym of pickpocket; that is, thief is a word with a broader meaning than pickpocket:

pickpocket: a thief who steals from the pockets or purses of others in public places
thief: a criminal who takes property belonging to someone else with the intention of keeping it or selling it

Other hypernyms of pickpocket include stealer.

pickpocket (noun)	thief (noun)
a thief who steals from the pockets or purses of others in public places	a criminal who takes property belonging to someone else with the intention of keeping it or selling it