preoccupation vs preoccupancy

preoccupation and preoccupancy both are nouns.

Word	Noun	Adjective	Verb	Adverb
preoccupation	Yes	No	No	No
preoccupancy	Yes	No	No	No

As nouns, preoccupation and preoccupancy are synonyms defined as:

preoccupation and preoccupancy: the act of taking occupancy before someone else does

As nouns, preoccupation and preoccupancy are synonyms defined as:

preoccupation and preoccupancy: the mental state of being preoccupied by something

Other synonyms of preoccupation include absorption, engrossment.

preoccupation (noun)	preoccupancy (noun)
the act of taking occupancy before someone else does	the act of taking occupancy before someone else does
the mental state of being preoccupied by something	the mental state of being preoccupied by something
an idea that preoccupies the mind and holds the attention