Final answer:
The italicized word 'as if' is a conjunction that connects clauses in a sentence.
Step-by-step explanation:
The italicized word 'as if' in the sentence 'Two horses galloped past the fence as if they owned the arena' is a conjunction. Conjunctions are words that connect other words or groups of words in a sentence. In this case, 'as if' connects the subordinate clause 'they owned the arena' to the main clause of the sentence.
Learn more about parts of speech