# Parameters and arguments: passing information to a function

[Concepts explained](README.md)

A function can do the same job with different information. Its **parameters** are the names in its definition. Its **arguments** are the values you supply when calling it.

Think of a recipe that says “use this many apples.” The blank in the recipe is like a parameter. Choosing four apples is like supplying an argument.

```pliro
# language: en
function total(price, amount):
    return price * amount
say total(3, 4)
```

`price` and `amount` are parameters. The arguments `3` and `4` give them values for this call. The answer is `12`.

## Order and number matter

Pliro matches arguments to parameters by position. The first goes into the first slot. A parameter's name does not automatically pull a same-named variable from somewhere else.

The number of arguments is sometimes called **arity**. This function needs two. Supplying one or three is an error. Built-ins document their permitted counts in their reference pages.

Pliro evaluates ordinary call arguments from left to right. Giving a function a list or map shares that collection; it does not automatically make a deep copy. The [mutation article](mutation.md) explains why that matters.

Try `total(5, 2)`, then explain the two parameter values before calculating the answer.

[Calls](../syntax/calls.md) · [Return values](return-values.md)