Hi Emar, I can't give you any rules, but I will try giving you a few examples. Over the years ... Something has changed over time ... In both cases, the time period could be either a long or relatively short period of time - but the length of the time period isn't defined. Throughout my time at college ... This is a specific period of time - the time that I was there. Throughout history ... I guess that's a specific period of time too, just a very long one!!

There really aren't any simple rules for which preposition to use in which situation. Some words are usually collocated with certain prepositions, but in some cases it can vary by country or even by region.

Interesting question! I can’t think of any cases where they are directly interchangeable. In general, ‘over’ talks about the result, ‘throughout’ the action. First, ‘over’ can be used for definite time periods. I painted my deck over the weekend. (There is a change - deck unpainted to deck painted) Over the years, he’s become more conservative. (Indefinite time period, changed status - less conservative then to more conservative now) She won more grand slams over the course of her career than any other woman in history. She checks Facebook throughout/during the day. (That’s what she does) Throughout her childhood, she went to church every Sunday. (Action) Over the course of her childhood, she went to church 700 times. (Some may drop ‘the course of’ here, but it sounds less accurate. Result) Over the years, I’ve watched a lot of television. (Not ‘I watched. I’m talking about the result ) She won 15 grand slams throughout/during/in her career.