Yes, since is a preposition (e.g. since noon).
It can also be a conjunction (since you arrived) or an adverb (gone ever since).
The prepositional phrase in "They haven't seen him since the party" is "since the party"
No.......... :'(
since the party
"In your backyard" is a prepositional phrase. The preposition is "in" and "backyard" is a noun, the object of the preposition.
which of these words is not a preposition past since join and except
for:)
The object of the prepositional phrase "during the Civil War" is the word "war" or since it is a proper noun, "Civil War."
The prepositional phrase is in the park. Camping is not part of the prepositional phrase.
In the wind is the prepositional phrase.
A prepositional phrase that modifies a noun or pronoun is an adjective prepositional phrase. An adjective prepositional phrase almost always follows the noun/pronoun it modifies.
Several has to be the subject since 'of the caves' is a prepositional phrase and 'are open' is the verb.
A second prepositional phrase in a sentence that modifies part of the first prepositional phrase. There can also be a third nested prepositional phrase that modifies part of the second prepositional phrase, and so on. For example: Mary ran (to the end (of the street.)) The first prepositional phrase is "to the end" and the second prepositional phrase is "of the street" where "of the street" modifies "end" so "of the street" is a nested prepositional phrase. I am excited (for the birthday party (for Ashley.)) The first prepositional phrase is "for the birthday party" and the second prepositional phrase is "for Ashley" where "for Ashley" modifies "birthday party" so "for Ashley is a nested prepositional phrase. A non-nested prepositional phrase would be a second prepositional phrase that does not modify part of the first prepositional phrase. For example: Mary ran (to the street) (in the morning.) The first prepositional phrase is "to the street" which modifies "ran." Mary ran to the street. The second prepositional phrase is "in the morning" which also modifies "ran." Mary ran in the morning.