What part of speech is the word old?

The word "old" can be a few different parts of speech depending on how it's used in a sentence:

* Adjective: This is the most common usage. Example: "The old house creaked in the wind."

* Noun: This is less common, but it can refer to a specific age or time period. Example: "The old times were simpler."

* Adverb: This is also less common, but it can modify verbs or adjectives to describe a state of being old. Example: "He looked old for his age."

It's important to look at the context to determine the specific part of speech.