Mode of acting or manifestation to the senses, or the
   intellect; as, water assumes the form of ice or snow. In modern usage,
   the elements of a conception furnished by the mind's own activity, as
   contrasted with its object or condition, which is called the matter;
   subjectively, a mode of apprehension or belief conceived as dependent
   on the constitution of the mind; objectively, universal and necessary
   accompaniments or elements of every object known or thought of.