Here's a simple example of some variable declarations and two function declarations:

function greeter(person: string): string {
  return "Hello, " + person;
}

function circumference(radius: number) : number {
  var pi: number = 3.141592654;
  return 2 * pi * radius;
}

var user: string = "Ray";

console.log(greeter(user));
console.log("You need " + 
circumference(2) + 
  " meters of fence for your dog.");

This example shows how to annotate functions and variables.

Variables—either standalone or as arguments to a function—are decorated using a colon and then the type. For example, the first function, greeter, takes a single argument, person, which must be a string. The second function, circumference...