Meaning of “begin” - Learner’s Dictionary

begin

verb uk us /bɪˈɡɪn/ (present participle beginning, past tense began, past participle begun)
START TO DO [ I, T ]

A2 to start to do something:

[ + doing sth ] Have they begun building the wall yet?
She began her career as a journalist on a local newspaper.
START TO HAPPEN [ I ]

A1 to start to happen:

What time does the film begin?
The war began at the end of August.
begin with sth

B1 to have something at the start:

Local phone numbers begin with 1223.
to begin with

B1 at the start of a situation:

To begin with, the two girls got on well.

B2 used to give the first important reason for something:

To begin with, we can't leave the children alone.

(Definition of “begin” from the Cambridge Learner’s Dictionary © Cambridge University Press)