deviation vs departure

deviation and departure both are nouns.

Word	Noun	Adjective	Verb	Adverb
deviation	Yes	No	No	No
departure	Yes	No	No	No

As nouns, deviation and departure are synonyms defined as:

deviation and departure: a variation that deviates from the standard or norm

Other synonyms of deviation include difference, divergence.

deviation (noun)	departure (noun)
deviate behavior	the act of departing
a turning aside (of your course or attention or concern)	euphemistic expressions for death
the error of a compass due to local magnetic disturbances	a variation that deviates from the standard or norm
the difference between an observed value and the expected value of a variable or function
a variation that deviates from the standard or norm