enter vs enter upon

enter and enter upon both are verbs.

Word	Noun	Adjective	Verb	Adverb
enter	No	No	Yes	No
enter upon	No	No	Yes	No

enter (verb)	enter upon (verb)
set out on (an enterprise or subject of study)	take possession of
make a record of; set down in permanent form
become a participant; be involved in
put or introduce into something
come on stage
to come or go into
take on duties or office
register formally as a participant or member
be or play a part of or in