Downstairs is a common word used to describe the lower level of a building or house. However, there are several synonyms that can be used to add variety to your writing. Some of the most common synonyms for downstairs include the cellar, basement, lower level, ground floor, and subterranean floor. Other synonyms include the underground, lower story, nethermost level, and bottom floor. Using synonyms can help spice up your writing and make it more interesting. Whether you're writing a novel, academic paper, or simply sending an email, make sure to choose a synonym that fits the tone and context of your message.