What part of speech is "and" in "Sarah and Christine are coming over my house"?

In the sentence "Sarah and Christine are coming over my house," "and" functions as a conjunction. Conjunctions are words that connect other words, phrases, or clauses. In this case, "and" is linking the two subjects, "Sarah" and "Christine," indicating that they are both involved in the action of coming over. This use highlights the role of conjunctions in coordinating elements of a sentence to express combined ideas or actions, making "and" an essential connective element in English grammar.