The term "next door" is used to describe a place or person that is located near or adjacent to your own. Some common synonyms for "next door" include "neighbor," "adjacent," "neighboring," "nearby," and "adjoining." Each of these words indicates proximity or close proximity to something or someone else. "Neighbor" is perhaps the most commonly used synonym, as it refers specifically to the person living next to you. "Adjacent" and "adjoining" describe things that are physically connected or touching each other. "Neighboring" and "nearby" both describe things that are close in proximity, but not necessarily touching or connected.