An expression is any combination of keywords, operators, functions, and constant values that result in a value of a given type. For example:
//An expression that evaluates to the Number value 25 10 + 20 - 5 //An expression that evaluates to the String value //"This is a string." "This is a string."
A Crystal syntax formula consists of a sequence of expressions. The value of the final expression is the value returned by the formula and what gets printed. Each expression must be separated from the previous expression by a semicolon (;).