The Collaborative International Dictionary of English v.0.48:

Schema \Sche"ma\, n.; pl. Schemata, E. Schemas. [G. See
   Scheme.] (Kantian Philos.)
   An outline or image universally applicable to a general
   conception, under which it is likely to be presented to the
   mind; as, five dots in a line are a schema of the number
   five; a preceding and succeeding event are a schema of cause
   and effect.
   [1913 Webster]