What part of speech is the word sour?

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

* Adjective: This is the most common usage, describing something that has a sharp, unpleasant taste or smell.

* Example: "The milk tasted sour."

* Verb: This refers to the action of becoming sour, or making something sour.

* Example: "The grapes soured in the heat."

* Noun: This is less common but can refer to the state of being sour, or a sour substance.

* Example: "The sour of the lemon juice made me pucker."

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