The difference between them is the difference that always exsists between 'the' and 'a'. Use 'the' when the person you are speaking knows which river (or thing) you are referring to. Typically this means that you have already mentioned it: "We spent our holiday at a hotel by a river. We swam in THE river every day." Or there is only one: My hometown is lovely. There are lots of bars and cafés by THE river. (The only river in the town.) Use 'a' when the person you are speaking to does not know which specific thing you are talking about. You just mean one of many: "I'd really like to live by A river " (I don't mind which one.) or you haven't told them yet which one: "We spent our holiday at a hotel by A river. We swam in the river every day."

The = definite article. We use "the" to talk about something specific or when there is only one of something. If there is only 1 river in your town, you would say THE river. A = indefinite article. We use "A" to refer to something not specific or general.

They mean the same thing but theyre used differently like for example, "hey do you want to go to the river" or "Theres a river over there" so theres really no difference its more like just knowing when it is the right time to use the words The and A

Hello, Ei Shwe Zin. I agree with Joe. It has to do with when to use which article. You would use "the" river when you need to be specific about it or if it is the only river. On the other hand, "a" river can be referring to any number of rivers or just rivers in general. I hope this explanations helps you better understand which article to use when describing rivers!