1. Unknown to most people

See also: unknown

• planetary house
• planetary nebula
• planetary science
• planetesimal
• planetesimal hypothesis
• planetoid
• planetology
• plangency
• plangent
• planimeter
• planing machine
• planish
• planisphere
• planispheric
• plank
• plank down
• plank over
• plank-bed
• planking
• plankton
• planktonic
• planktonic algae
• planless
• planned
• planned community