A keyword is used where it has no meaning. Examples of these are using the param keyword outside a settings section, or using one of the conditional keywords inside an expression.
z = if (1) z = repeat + 3
In the last example, it looks like repeat was meant as a variable. This is not possible, so you should rename it.
This error is also generated if the this keyword is used outside a class, or from a static method.
See Also
Errors