val variables and var variables

## val variables and var variables

Kotlin has two different kinds of variables: val variables and var variables. val stands for value, and a val variable can never change its value. Once you have defined it, its value will always remain the same:

val m = 17
m = 18      // error!

A var variable, on the other hand, can change its value as often as you want:
var n = 17
n = 18      // ok


val variables do not exist in Python, C, C++, or Java. They belong to a style of programming called functional programming, and exist in programming languages such as LISP (perhaps you have met the let command of Scheme and Racket), Scala, Haskell, ML, etc.