Both sentences are grammatically correct, but they have slightly different meanings. "The dog ran quickly" refers to a specific dog that ran quickly, while "A dog ran quickly" refers to any dog that ran quickly. The use of "the" implies specificity, while the use of "a" implies generality.
The phrase "ran very quickly" consists of a verb ("ran") and an adverb ("very quickly").
Quickly is an adverb. It describes a verb. e.g. The man ran quickly along the road. In this case ran is the verb and quickly is the adjective as it describes the manner in which the man ran.
She ran quickly around the tree is a sentence, or a clause. Quickly is an adverb. It gives us more information about the verb ran.
It means sprinted or ran quickly.
quickly
It means the dog ran in the past
A simile for quickly is he/she ran so quickly it seemed as if someone was chasing him/her!!!
Since it is the description of an action word, yes. Such as: She ran quickly. "ran" - is an action word (verb) and "quickly" describes it.
quickly
EX. "He ran very quickly to his house."
Adverbs are used to modify verbs, adjectives, and other adverbs. For example:'My cousin ran quickly' (quickly modifies the verb ran);'Her speed was very fast' (very modifies the adjective fast);'You could say that she ran extremely quickly' (extremely modifies the adverb quickly).