penniless vs impecunious

penniless and impecunious both are adjectives.

Word	Noun	Adjective	Verb	Adverb
penniless	No	Yes	No	No
impecunious	No	Yes	No	No

As adjectives, penniless and impecunious are synonyms defined as:

penniless and impecunious: not having enough money to pay for necessities

Other synonyms of penniless include hard up, in straitened circumstances, penurious, pinched.

penniless (adjective)	impecunious (adjective)
not having enough money to pay for necessities	not having enough money to pay for necessities