In TypeScript, you can declare a variable using the `let` or `const` keyword, just like in JavaScript. However, TypeScript also allows you to specify the variable type using type annotations. Here are a few examples:

// Declaring a variable with a type annotation
let myNumber: number = 42;

// Declaring a variable without a type annotation
let myString = "Hello, world!";

// Declaring a constant with a type annotation
const PI: number = 3.14;

// Declaring a variable with an array type
let myArray: string[] = ["apple", "banana", "orange"];

// Declaring a variable with an object type
let myObject: { name: string, age: number } = { name: "Alice", age: 30 };

In the first example, we declare a variable `myNumber` of type `number` and assign it the value `42`. In the second example, we declare a variable `myString` and TypeScript infers its type to be `string` based on the value `"Hello, world!"`. In the third example, we declare a constant `PI` of type `number` and assign it the value `3.14`. In the fourth example, we declare a variable `myArray` of type `string[]`, which is an array of strings. We initialize it with an array of string values. In the fifth example, we declare a variable `myObject` with an object type that has two properties: `name` of type `string` and `age` of type `number`. We initialize it with an object that has these properties and their corresponding values. Note that in TypeScript, you can also declare variables using the `var` keyword, but it's generally recommended to use `let` or `const` instead, as they have more predictable scoping rules.