adj.
  - most suitable; perfect.
 - desirable or perfect but existing only in the imagination:
 in an ideal world.
 ▸representing an abstract or hypothetical optimum.
 
n.
 a person or thing regarded as perfect. 
▸a standard or principle to be aimed at.
 
  Derivative
  
  Etymology
  ME (as a term in Platonic philosophy, in the sense ‘existing as an archetype’): from late L. idealis, from L. idea (see idea).