Bathypelagic, also known as abyssal or deep-sea, refers to the layer of water that ranges from 1,000 to 4,000 meters below the ocean's surface. Synonyms for bathypelagic can be used interchangeably based on the context they are used in. These synonyms include aphotic, midnight, and dark zone. The aphotic zone implies areas with no light penetration, while the midnight zone suggests a layer where darkness prevails, and the dark zone describes areas with low-light levels. Other synonyms for bathypelagic include benthic, abyssopelagic, and hadopelagic. These terms further classify the ocean depth zones, helping to define the unique environments and ecosystems found in these zones.