What type of verb is barked in the sentence dog barked?

"Barked" in the sentence "Dog barked" is an action verb.

Here's why:

* Action verbs describe actions that someone or something does. In this case, the dog is performing the action of barking.

* Transitive verbs require a direct object (the thing being acted upon). "Barked" is an intransitive verb because it doesn't have a direct object. The dog simply barked, we don't know at what or whom.