semi vs semitrailer

semi and semitrailer both are nouns.

Word	Noun	Adjective	Verb	Adverb
semi	Yes	No	No	No
semitrailer	Yes	No	No	No

As nouns, semi and semitrailer are synonyms defined as:

semi and semitrailer: a trailer having wheels only in the rear; the front is supported by the towing vehicle

semi (noun)	semitrailer (noun)
a trailer having wheels only in the rear; the front is supported by the towing vehicle	a trailer having wheels only in the rear; the front is supported by the towing vehicle
a truck consisting of a tractor and trailer together
one of the two competitions in the next to the last round of an elimination tournament