interrelation vs interrelationship

interrelation and interrelationship both are nouns.

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

As nouns, interrelation and interrelationship are synonyms defined as:

interrelation and interrelationship: mutual or reciprocal relation or relatedness

Other synonyms of interrelation include interrelatedness.

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