The rule the function normally applies seems to be limited and does not hold for all inputs. For some words, such as "Wolf", the function assigns the label "Italian". However, for other words like "Greece", "Lena", "Rhine", "Portugal", "Marco Rubio", "Spain", and "Ankara", the function does not seem to apply any rule and the output is undefined. Therefore, the domain of the function where the rule normally applies is limited and not all words will result in a defined output.