In Ruby, constants must be assigned a value when they are declared. If a constant is referenced without being assigned a value, Ruby will raise a "NameError" indicating an "uninitialized constant" [2][3]. This error occurs because Ruby constants are expected to be defined with a value before they are used. Unlike some other programming languages where constants or variables might be automatically initialized to a default value (like null or 0), Ruby requires explicit initialization of constants.
For example, attempting to use a constant without initializing it, like this:
