begin 最常用词，含义广泛，其反义词是end，多用于行动、工作等的开始。
start 在许多场合可与begin通用，但start侧重动作的起点。
commence 可与begin换用，但commence系书面正式用词，语气庄重，特指有正式程序或一定仪式，或某种正式行动的“开始”。
initiate 指创始或发起，侧重某过程的第一步，不考虑结束，强调起始。
inaugurate 指正式而隆重的开始。
参考例句
1. The bus will start at 7:30 tomorrow morning. 汽车将于明晨7时30分准时开出。
2. All: Yes, we should start to work. 大家：是的，我们要开始工作了。
3. Dante: Now I can start my business. 但丁：现在我可以开始营业了。
英英解释
n.
1. the beginning of anything
2. the time at which something is supposed to begin
3. a turn to be a starter (in a game at the beginning)
4. a sudden involuntary movement
5. the act of starting something
6. a line indicating the location of the start of a race or a game
7. a signal to begin (as in a race)
8. advantage gained by an beginning early (as in a race) v.
1. take the first step or steps in carrying out an action
2. set in motion, cause to start
3. leave
4. have a beginning, in a temporal, spatial, or evaluative sense
5. bring into being
6. get off the ground
7. move or jump suddenly, as if in surprise or alarm
8. get going or set in motion
9. begin or set in motion
10. begin work or acting in a certain capacity, office or job
11. play in the starting lineup
12. have a beginning characterized in some specified way
13. begin an event that is implied and limited by the nature or inherent function of the direct object
14. bulge outward
