A periodontist is a dentist who specializes in the prevention, diagnosis, and treatment of periodontal disease, and in the placement of dental implants. Periodontists are also experts in the treatment of oral inflammation.
Ground speed. Ground speed is the horizontal speed of an aircraft relative to the ground. An aircraft heading vertically would have a ground speed of zero. Information displayed to passengers through the entertainment system often gives the aircraft ground speed rather than airspeed.
Driving too fast for conditions is generally driving at a speed which impairs a driver's ability to negotiate curves or maneuver around obstacles in the roadway, extends the distance necessary for a vehicle to stop, and increases the distance a vehicle travels while the driver reacts to a hazard.