IPA: /ˈlɑː.sən.ɪst/
KK: /ˈlɑr.sə.nɪst/
A person who steals someone else's property.
The police arrested the larcenist after he was caught stealing from a store.
Larcenist → It is formed from "larceny" (from Old French *larciner*, meaning theft) and the suffix "-ist" (meaning one who practices or is concerned with). A larcenist is someone who practices theft or engages in stealing.
Think of a 'larceny' as a form of theft, and remember that a 'larcenist' is someone who is involved in that act of stealing.
No commonly confused words.