"The dog" isn't a sentence because it doesn't have a verb.
If you are asking what part of speech it is, "the" is an article, and "dog" is a noun.
It is a declarative sentence.
exclamatory
The sentence contains a compound sentence.
transitive
Our cat and dog love to play together every single night.
Yes you can Example : The Doberman was barking at me (Doberman:a type of dog)
A verb is something you do, for example, "run", "jump", etc. "Bark" would be the verb in the sentence, "The dog barked."
A preposition is a type of dog. They don't go in the beginning of the sentences
"The dog" is a noun phrase that serves as the subject of a sentence, but it is not a complete sentence by itself. A simple sentence requires both a subject and a predicate, such as "The dog barks." In this case, "the dog" functions as the subject of the simple sentence.
Yes, a dog is a subject if your talking to someone about your dog, the dog would be the subject you are talking about.
the dog
'There is a dog' is the complete subject of the sentence. It consists of the subject 'dog' and the linking verb 'is'.