είδος

Etymology: From Ancient Greek εἶδος (eîdos) meaning 'form, shape, figure, appearance'. This term has philosophical significance in Platonic thought, where it referred to the 'ideal form' or 'essence' of something. The English words 'idea' and 'idol' derive from the same Greek root, as does the scientific suffix '-oid' (meaning 'resembling'). The term evolved from its original meaning of 'that which is seen' (from the verb εἴδω, 'to see') to encompass classifications and categories.