expressionless vs impassive

expressionless and impassive both are adjectives.

Word	Noun	Adjective	Verb	Adverb
expressionless	No	Yes	No	No
impassive	No	Yes	No	No

As adjectives, expressionless and impassive are synonyms defined as:

Other synonyms of expressionless include deadpan, poker-faced, unexpressive.

expressionless (adjective)	impassive (adjective)
deliberately impassive in manner	deliberately impassive in manner
	having or revealing little emotion or sensibility; not easily aroused or excited