infelicitous vs unhappy

infelicitous and unhappy both are adjectives.

Word	Noun	Adjective	Verb	Adverb
infelicitous	No	Yes	No	No
unhappy	No	Yes	No	No

As adjectives, infelicitous and unhappy are synonyms defined as:

infelicitous (adjective)	unhappy (adjective)
not appropriate in application; defective	experiencing or marked by or causing sadness or sorrow or discontent
marked by or producing unhappiness	generalized feeling of distress
	marked by or producing unhappiness
	causing discomfort