Morphē

From the Greek morphē — the essential, underlying nature or form of a thing: what it actually is, beneath any surface arrangement. Unlike schēma (the changeable outward fashion), morphē is the substance that surface adjustment cannot reach — the form a thing truly has, as when Christ existed “in the form (morphē) of God” (Philippians 2:6). Synonyms: essential form, underlying nature, substance.

See also: The Mask and the Metamorphosis