Plaque

Plaque: a word meaning a flat, plate-like object.

• Plaque in biology is
  • a growth-form, as, for example, the growth of bacterial colonies on an agar plate.
  • a sticky, white film or fluid on the teeth. It is a mixture of bacteria and food. It causes tooth decay. It is very harmful for teeth.

• A flat man-made object such as a commemorative or memorial plaque, or other flat object.