* Adjective: This is the most common usage. It describes a noun, meaning "lacking manners or consideration." For example: "He was being rude to the waiter."
* Noun: It can be used as a noun to refer to an instance of bad behavior. For example: "He said some real rudes."
* Verb: It can also be used as a verb, meaning "to treat someone rudely." For example: "She was ruding me by interrupting constantly."
The part of speech depends on the context of how the word is being used.