A variable is a name given to some value. Variable names can contain lowercase and uppercase letters, digits, underscores (_) and apostrophes, with the only restriction that a name must start with a letter. For example, myHorse3, some_name, and X__17'x'_ are all valid variable names.

To define a variable, one must first use a type signature to declare its type on a line by itself, like

variable_name : type

where type is replaced by whatever type the variable should have. The value of the variable can then be defined using an = sign, like

variable_name = expr

where expr represents an arbitrary expression. (There is also special syntax available for defining functions.) For example:

my_variable : Z
my_variable = 2 * 7 + 9

The above code defines the variable my_variable with the type Z (i.e. an integer) and the value 23.