**In mathematics:** a value that is more "built in" to a function. It is similar to a variable, but stays fixed while we use the function.

Example: in this function for the height of a tree the "20" is a parameter:

**h(year) = 20 × year**

We can change the parameter!

Example: A different tree's growth rate is 30 cm per year, so its function is **h(year) = 30 × year**

We could even make it more general by writing

**h(age, rate) = rate × age**

**In software:** it is the name given to the values that are passed in to a function.

Example: in this function, "val" is a parameter:

function double(val) {

return val*2

}

When we call the function such as double(7), then "7" is called an argument.