petty vs thieving

petty and thieving both are nouns.

Word	Noun	Adjective	Verb	Adverb
petty	Yes	Yes	No	No
thieving	Yes	Yes	No	No

As nouns, thieving is a hypernym of petty; that is, thieving is a word with a broader meaning than petty:

petty: larceny of property having a value less than some amount (the amount varies by locale)
thieving: the act of taking something from someone unlawfully

Other hypernyms of petty include larceny, stealing, theft, thievery.

petty (noun)	thieving (noun)
larceny of property having a value less than some amount (the amount varies by locale)	the act of taking something from someone unlawfully

petty (adjective)	thieving (adjective)
inferior in rank or status	given to thievery
contemptibly narrow in outlook
(informal) small and of little importance