• Commemorative plaque, a flat ornamental plate or tablet fixed to a wall, used to mark a significant event, person, etc.
• Memorial plaque, issued to next-of-kin of dead British military personnel after WWI
• Plaque, a rectangular Casino token

In biology:

• Dental plaque, a biofilm that builds up on teeth
• Atheromatous plaque, a buildup of fatty deposits within the wall of a blood vessel
• Mucoid plaque, a supposed thick coating of abnormal mucous material in the colon
• Viral plaque, a visible structure formed by virus propagation within a cell culture
• Senile plaques, an extracellular protein buildup implicated in various diseases like Alzheimer's disease or Parkinson's disease
• Plaque, a (usually) small, disk-shaped growth, common in some forms of skin cancer
• Pleural plaque, pleural fibrosis, often caused by exposure to asbestos

See also

• Placard, a poster
• Plack, an ancient Scottish coin