please, when we use "to start" and when we use "to begin" ?
People, and most dictionaries, consider start and begin to be synonyms, as in the following pairs of sentences:
(a) It’s starting to rain.
(b) It’s beginning to rain.
(c) When Katherine heard the news, she started to cry.
(d) When Katherine heard the news, she began to cry.
(e) The movie starts at 7:00.
(f) The movie begins at 7:00.
However, The American Heritage Dictionary of the English Language (Houghton Mifflin, 1996) notes that only start, not begin, can imply setting out from a specific point, frequently following inaction, as in sentence (g) below:
(g) Stand here and visit with me for a few minutes until the train starts.
The same source notes that begin often means to take the first step in performing or to come into being.
Michael Swan (Practical English Usage, 2nd ed., Oxford University Press, 1995) lists these instances in which start, but NOT begin, is used:
start a journey: I think we ought to start at six, while the roads are empty.
start working (for machines): The car won’t start.
make (machines) start: How do you start the washing machine?
So, while in most instances start and begin are interchangeable, in a few cases, such as those described above, only start is possible.
To start can be used with machines such as computers, cars, etc. It might also referr to something that is going to be long, but it does not suggests when are you going to make it: I'm going to start the computer. I'm going to start an essay (soon).
To begin is more speciffic: I'm going to begin with my essay (now, next week, whatsoever).
To get underway is used with long thing that need a process, but it expresses some willing, not very speciffic in time: We are going to get our proyect underway (as soon as we can).