Here's how it works:
* Adjective: The most common use of "bold" is as an adjective, describing something as daring, strong, or striking. For example: "She made a bold statement with her outfit."
* Noun: "Bold" can also be a noun, referring to a type of typeface that is thick and dark. For example: "The headline was set in bold type."
So, whether "bold" is a noun or an adjective depends on its context in the sentence.