NameError

        # NameError < StandardError

(from ruby core)
---
Raised when a given name is invalid or undefined.

    puts foo

*raises the exception:*

    NameError: undefined local variable or method `foo' for main:Object

Since constant names must start with a capital:

    Integer.const_set :answer, 42

*raises the exception:*

    NameError: wrong constant name answer
---
# Class methods:

    new

# Instance methods:

    local_variables
    name
    receiver