 In this video, we're going to talk about function declarations and function expressions in TypeScript. Function declarations and function expressions in TypeScript are similar with JavaScript function declarations and expressions. So in TypeScript, you can declare a function with its name. For example, let's make a function, let's call it multiplication. And in TypeScript, we need to provide types for our parameters and types for our returning value. The parameters of our function is going to have number type and the returning value of our function is going to be number. So we want to return the multiplication of those two variables X and Y. And this first function is a function declaration. So we can call it that this is a function declaration. That's the first way to make a function in TypeScript. On the other way, we can declare a function without its name. For example, let's make a variable multiply and let's make an anonymous function, which is going to do the same exact thing to multiply two numbers, which we would be given as parameters of the function and returning value is going to be a number. So it's almost the same code, but these two functions are a little bit different. This one is a function expression. These two functions are very similar, but they behave differently. You can call the first function multiplication before it's been declared. So you can, for example, set a console.log and call this multiplication function with few provided parameters. We need to provide X argument and Y and you can do this with your function declaration. You can call it before you declare it. But on the other way, with function expression, you can call it before your expression is not finished. For example, if you try to call in the same way this function expression by using this variable multiply and provide the same arguments as in the first function multiplication. If you try to convert your code to JavaScript and run it into your browser, you will get an error because you can't use this function before this expression is not finished. So if you want to use this function, you need to call it after this expression. And on the other way, function declaration, function multiplication, you can call it everywhere. You can call it before this function declaration or you can call it after this function declaration. It doesn't matter. Okay, that's all in this lesson. Don't forget to subscribe to my channel. See you in the next video. Bye.