Plaque (noun)

1. A flat, typically circular object with a raised surface, used to commemorate an event or person.
2. A flat, usually decorative, plate or tablet fixed to a wall or monument.
3. A thin, flat layer or deposit of material, such as bacteria or fat, that forms on a surface.

Origin:

Mid 18th century: from french, from old french plache, from medieval latin placca, of germanic origin; related to dutch plak and german plakette.

Examples:

1. The plaque on the wall honored the town's founding fathers.
2. The plaque was unveiled on the anniversary of the battle.
3. The plaque on the tooth is caused by bacteria and can lead to cavities.
4. The plaque build up in the artery can lead to heart attack or stroke.
5. The plaque on the monument was dedicated to the memory of the fallen soldiers.