Prep vs Preparatory - What's the difference?

As an initialism prep

is (emergency medicine) initialism of pre-exposure prophylaxis .

of or pertaining to preparation, having the purpose of making something or someone ready, preparative.

(countable) Preparation.

(informal, countable) A student or graduate of a prep school, a preppy.

(British, uncountable) Homework, work set to do outside class time, used widely in public schools and preparatory schools but not state schools.

(prepp)

(informal) To prepare.

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of or pertaining to preparation, having the purpose of making something or someone ready, preparative

I will conduct some preparatory research before choosing the new restaurant's location.

*preparatory school *preparatorily