Okay kiddo, you know how when you have apples, and you add more apples, you end up with more apples than you started with? That’s kind of like an addition theorem!
An addition theorem is just a fancy math term for when you add two things together and end up with a new thing that’s bigger than either of the things you started with.
For example, if you have 2 toy cars and you get another 3 toy cars, you can add them up and see that you now have 5 toy cars! That’s because of the addition theorem.
In math, there are specific rules you have to follow when you’re adding things up, like you always have to start with the number 0 and you can only add one number at a time. These rules can help make sure you get the right answer every time you use an addition theorem.
So, that’s what an addition theorem is - it’s a way to add things together to get a new, bigger thing!