Longman Dictionary of Contemporary English - begin

past tense began past participle begun v 1 »START DOING/FEELING« to start doing something or start feeling a particular way  (begin to do sth)  (We began to wonder if the train would ever arrive. | begin)  (I'll begin when you're ready. | begin sth)  (She curled up in bed and began her book. | begin doing sth)  (I left teaching in 1990 and began working in my present job. | begin by doing sth (=do or say something as the first part of an activity))  (Can I begin by thanking you all for being here tonight?) 2 »START HAPPENING« if something begins, or you begin something, it starts to happen or exist  (Work on the new bridge will begin next year. | It was the coldest winter since records began.) + a  (The meeting begins at 10.30 am.) begin (sth) as  (Roger began his career as a model.) 3 to begin with a) especially spoken used to introduce the first or most important point that you want to make  (Well, to begin with, he shouldn't even have been driving my car.) b) used to say that something was already in a particular condition before something else happened  (I didn't break it! It was like that to begin with.) c) during the first part of a process or activity  (The kids helped me to begin with, but they soon got bored.)  (- see firstly) 4 »SPEECH/BOOK« if a speech, book, word etc begins with something, it starts with a particular event, activity, letter etc  (`Psychosis' begins with a P.) 5 can't begin to understand/imagine etc spoken used to emphasize how difficult something is to understand etc  (I can't begin to imagine how awful it must be to lose your child.)