interrelationship vs interrelation

interrelationship and interrelation both are nouns.

Word	Noun	Adjective	Verb	Adverb
interrelationship	Yes	No	No	No
interrelation	Yes	No	No	No

As nouns, interrelationship and interrelation are synonyms defined as:

interrelationship and interrelation: mutual or reciprocal relation or relatedness

Other synonyms of interrelationship include interrelatedness.

interrelationship (noun)	interrelation (noun)
mutual or reciprocal relation or relatedness	mutual or reciprocal relation or relatedness