Genasi

A genasi is a humanoid that has a genetic heritage of both mortal humanoid and some sort of Elemental creature (usually a Genie or humanoid elemental-kin). Examples include:

• Wind+dukes- humanoid and air entity (Djinni, sylph, etc.)
• Stone+princes - humanoid and earth entity (Dao, pech, etc.)
• Flame+lords - humanoid and fire entity (Efreeti, fire spirit, etc.)
• Sea+kings - humanoid and water entity (Marid, Nereid, etc.)
• Other types with a Paraelemental or Quasielemental heritage exist, but the four above are the most common types of genasi

Genasi tend to be arrogant and aloof, associating their superiority with their elemental heritage. They generally do not get along with others, even those of their own genasi type.

Source: The Planewalker's Handbook, Player's Guide to Faerun, Monsters of Faerun

See also The Planar Handbook (mephlings)