Airfoil (aerofoil): a wing, kite, or sail used to generate lift or propulsion.
Airtime: the amount of time spent in the air while jumping. Airtime is also a brand name for a company that specializes in kite repair.
Angle of Attack (AOA) or Angle of Incidence (AOI): the angle with which the kite flies in relation to the wind. Increasing AOA/AOI generally creates more lift.
Apparent wind (AW): The wind speed felt by the kite or rider as it passes through the air. The apparent wind direction shifts towards the direction of travel as speed increases. AW can be increased or decreased by such things as current, water movement or movement of the rider/kite.
Aspect Ratio (AR): the ratio of a kites width (span) to height (chord). Kites generally have a high aspect ratio or a low aspect ratio. Low aspect ratio kites usually fly slower, are easier to relaunch, and have a more grunty downwind pull. High AR kites travel faster and fly further to the front of the window. This gives you better upwind ability, higher jumps and bigger wind range.