Over

In the sentence "The cat jumped over the fence," the word "over" is the preposition. A preposition is a word that typically indicates the relationship between its object (in this case, "the fence") and another element in the sentence (in this case, "jumped"). Prepositions often show location, direction, time, or other relationships. In this sentence, "over" indicates the direction of the cat's movement in relation to the fence. It tells us that the cat's action of jumping was in a direction that took it from one side of the fence to the other. Therefore, "over" is functioning as a preposition here.