> For the complete documentation index, see [llms.txt](https://shopify-1.gitbook.io/typescript/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shopify-1.gitbook.io/typescript/beginner/union-types.md).

# Union types

Most simple functions only expect arguments of a specific type. For example, `square()` would expect a `number`, `pluralize()` would expect a `string` and so on. But when you get into situations where the arguemnts are evaluating something like payment methods, things get a bit more complicated.

```typescript
function processPayment(method) {
    // ...
}
```

Say we have three different payment methods: `Cash`, `PayPal` and `CreditCard`, how do we type the `method` argument to allow for all three? By using a union, denoted by the pipe or vertical bar (`|`) character:

```typescript
function processPayment(method: Cash | PayPal | CreditCard) {
    // ...
}
```

We can simplify our example by combining the different payment method types into a named `type`:

```typescript
type PaymentMethod = Cash | PayPal | CreditCard;

function processPayment(method: PaymentMethod) {
    // ...
}
```