Hi - yes, usually they are interchangeable, although
begin can sometimes seem slightly more formal. But only as verbs with the meaning
commence. In other contexts they're different :
- You can only use start with the meaning set in motion for a car or other machine : My car won't start
- Only start can be a phrasal verb : We started off OK / He's starting up his own companyAs nouns start and beginning can't always be alternatives - for example, in set phrases like The beginning of the end
- Starter and Beginner are never alternatives - they have quite different meanings. A beginner = a person inexperienced in the field; a starter = the person who starts a race; the first course of a meal; the thing you use to start a car. Then there's the expression For starters (= first of all)