noun

• (countable) Any flat, thin piece of clay, ivory, metal, etc., used for ornament, or for painting pictures upon, as a dish, plate, slab, etc., hung upon a wall; also, a smaller decoration worn by a person, such as a brooch.
• (countable) A piece of flat metal with writing on it, attached to a building, monument, or other structure to remind people of a person or an event.
• (countable) A small card representing an amount of money, used for betting in casinos; a sort of gaming chip.
  "But on this June evening when Bond walked through the 'kitchen' into the salle privée, it was with a sensation of confidence and cheerful anticipation that he changed a million francs into plaques of fifty mille and took a seat […]"
• (countable, biology) A clearing in a bacterial lawn caused by a virus.