What part of speech is fast?

"Fast" can be several parts of speech, depending on how it's used in a sentence:

* Adjective: Describing something that moves or happens quickly.

* Example: "The cheetah is a fast runner."

* Adverb: Modifying a verb, adjective, or other adverb to indicate speed or quickness.

* Example: "She ran fast to catch the bus."

* Noun: Meaning a period of abstaining from food or drink.

* Example: "He is on a fast to lose weight."

* Verb: To abstain from food or drink.

* Example: "The doctor advised her to fast for a day."

So, without context, it's impossible to tell exactly which part of speech "fast" is.