prelim vs preliminary examination

prelim and preliminary examination both are nouns.

Word	Noun	Adjective	Verb	Adverb
prelim	Yes	No	No	No
preliminary examination	Yes	No	No	No

As nouns, prelim and preliminary examination are synonyms defined as:

prelim and preliminary examination: an examination taken by graduate students to determine their fitness to continue

Other synonyms of prelim include preliminary exam.

prelim (noun)	preliminary examination (noun)
an examination taken by graduate students to determine their fitness to continue	an examination taken by graduate students to determine their fitness to continue
a minor match preceding the main event