10. Bird means an animal which is neither a mammal nor a reptile. Which lexical rule is violated by this definition?

The lexical rule violated by this definition is the rule of mutual exclusivity. This rule states that the categories in a classification system should be mutually exclusive, meaning that an item can only belong to one category. In this case, the definition of a bird as an animal that is neither a mammal nor a reptile violates this rule because a bird can be classified as a type of animal, which includes both mammals and reptiles.