obsession vs compulsion

obsession and compulsion both are nouns.

Word	Noun	Adjective	Verb	Adverb
obsession	Yes	No	No	No
compulsion	Yes	No	No	No

As nouns, obsession and compulsion are synonyms defined as:

obsession and compulsion: an irrational motive for performing trivial or repetitive actions, even against your will

obsession (noun)	compulsion (noun)
an unhealthy and compulsive preoccupation with something or someone	using force to cause something to occur
an irrational motive for performing trivial or repetitive actions, even against your will	an irrational motive for performing trivial or repetitive actions, even against your will
	an urge to do or say something that might be better left undone or unsaid