In the English language, there are a lot of words that sound really similar, but they mean different things. And one example is the word then and the word than. Oftentimes we use them interchangeably, because they sound so similar, but they mean different things. And here's a way for you to remember the difference. Then equals time. So whenever we're talking about time or progression through time, we need to use the word then. And than equals comparison. Whenever we're comparing two things, we need to use the word than. I like memory tricks, and I remember this by noting that there's an E in then and time. And there's an A in than and comparison. It can just kind of help me recall it a little more quickly.
Let's take a look at how it functions in a sentence. Let's say, "I'm teaching a class, then going to a movie." Why did I use the word then with an E? Well the reason is because I'm talking about time. I'm teaching a class first. Then later, I'm going to a movie. So that's why we use the word then with an E. But if I want to say something like, "I'm taller than you are," well now I'm making a comparison. There's no time element here. I'm simply saying that I possess one quality more than you do. Because it's a comparison, we use the word than with an A. And that's the difference between then and than.