The word "in" is a preposition that is commonly used to indicate something is located inside a space or time frame. There are several synonyms for the word "in" that can be used to express the same meaning. Some of these synonyms are "inside," "within," "interior," "inward," "indoors," "enclosed," "contained," "surrounded," "enveloped," and "immersed." These words can be used interchangeably with "in" in many contexts to provide a more precise or varied description. For example, instead of saying "in the box," one can say "enclosed within the box," or "contained inside the box".