in straitened circumstances vs penniless

in straitened circumstances and penniless both are adjectives.

Word	Noun	Adjective	Verb	Adverb
in straitened circumstances	No	Yes	No	No
penniless	No	Yes	No	No

As adjectives, in straitened circumstances and penniless are synonyms defined as:

in straitened circumstances and penniless: not having enough money to pay for necessities

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

in straitened circumstances (adjective)	penniless (adjective)
not having enough money to pay for necessities	not having enough money to pay for necessities