What part of speech is decade?

"Decade" can be a few different parts of speech, depending on how it's used in a sentence:

* Noun: This is the most common usage. It refers to a period of ten years.

* Example: "The 1990s were a decade of rapid technological advancements."

* Adjective: It can describe something that lasts for ten years.

* Example: "The project will span a decade-long period."

* Adverb: While less common, it can modify a verb or adjective to indicate a duration of ten years.

* Example: "They have been living in this house decade-long." (This usage is less formal and might not be preferred in all contexts).