on

/ˈȯn/

Middle English an, on, preposition & adverb, from Old English; akin to Old High German ana on, Greek ana up, on

preposition

  1. —used as a function word to indicate position in contact with and supported by the top surface of

  2. —used as a function word to indicate position in or in contact with an outer surface

  3. —used as a function word to indicate position in close proximity with

adverb

  1. in or into a position of contact with an upper surface especially so as to be positioned for use or operation

  2. in or into a position of being attached to or covering a surface; especially : in or into the condition of being worn

  3. forward or at a more advanced point in space or time

put the plates on

adjective

  1. engaged in an activity or function (such as a dramatic role)

  2. being in operation

  3. placed so as to permit operation