Merfolk

Known by many names, merfolk are an aquatic species of magical people. Though they are not included in the category of magic-capable species, merfolk are certainly capable of some magical feats. Most notable among these is their standard method of communication, a type of telepathy-like magic unique to their species. In addition, most modern merfolk also know sign languages, used to communicate with merfolk incapable of telepathy, or with other species.

Basic Information

Anatomy

Though parts of their bodies look human-like, merfolk are fishes and anatomically resemble them, though they are difficult to classify precisely. They are facultative air breathers, and can breathe air by inhaling through the nose and passing spent air through the gills, but don't need to breathe air. They possess paired lungs similar to tetrapods, but also like lungfish and bichirs, both air-breathing fish.
Merfolk have diverse internal anatomy, as they are capable of surviving in both salt- and freshwater, which require different adaptations.

Dietary Needs and Habits

Merfolk are omnivorous, but feed primarily on fish. Depending on the community, they may farm or forage for the herbivorous part of their diet, and may hunt or farm for the fish. They may also feed on other aquatic animals, and surface-level merfolk may even hunt seabirds.
Freshwater merfolk diets are often more diverse and dependent on environment, and they often include more mammals and other land animals.

Additional Information

Perception and Sensory Capabilities

Like their anatomy, merfolk have senses similar to 'regular' fishes. Their eyes are similar to those of humans, and they possess color vision. Their ears are poorly developed, but they possess a lateral line, which can detect currents, vibrations, and motion, which is also considered a sense of hearing. They have chemoreceptors, granting them an excellent sense of smell and taste.

Civilization and Culture

Major Language Groups and Dialects

Merfolk communicate primarily with their own unique communication method, a type of magic which resembles telepathy. Using said telepathy, they communicate in memory fragments, emotions, and other such wordless feelings. Because this communication doesn't use words, merfolks have no separate languages and little to no linguistic shift, allowing them to communicate with other members of their species without language barriers.
Aside from their magical communication, most merfolk also know at least one sign language, though these vary per community. Some groups have their own sign languages, whereas others have simply taken one (or more) language from land-people.