begin vs start up

begin and start up both are verbs.

Word	Noun	Adjective	Verb	Adverb
begin	No	No	Yes	No
start up	No	No	Yes	No

As verbs, start up is a hyponym of begin; that is, start up is a word with a more specific, narrower meaning than begin:

begin (verb)	start up (verb)
take the first step or steps in carrying out an action	get off the ground
set in motion, cause to start	get going or set in motion
begin to speak or say
begin to speak, understand, read, and write a language
achieve or accomplish in the least degree, usually used in the negative
begin an event that is implied and limited by the nature or inherent function of the direct object
have a beginning, in a temporal, spatial, or evaluative sense
be the first item or point, constitute the beginning or start, come first in a series
have a beginning characterized in some specified way
have a beginning, of a temporal event