V Speeds

V1: Takeoff decision speed.
The maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.
VR: Rotation speed.
V2: Takeoff safety speed.
The minimum speed that must be attained after an engine failure at Vef and maintained throughout the second segment of takeoff, from 35 ft above the runway up to acceleration altitude. Provides essentially the best angle of climb for a one-engine inoperative condition.
V2min: Minimum takeoff safety speed.
Va: Design maneuvering speed.
Vb: Design speed for maximum gust intensity.
Vc: Design cruising speed.
Vd: Design diving speed.
Vdf / Mdf: Design diving speed.
Vef: The speed at which the critical engine is assumed to fail during takeoff.
Vf: Design flap speed.
Vfe: Maximum flap extended speed.
Vfs: Final segment takeoff speed.
Vfto: Final takeoff speed.
Vh: Maximum speed in level flight with maximum continuous power.
Vmc: Minimum control speed with the critical engine inoperative.
Vmo/Mmo: Maximum operating limit speed (Vmo) and Mach number (Mmo).
Vref: Reference landing speed.
Vs: The stalling speed or the minimum steady flight speed at which the airplane is controllable.
Vs0: The stalling speed or the minimum steady flight speed in the landing configuration. In small airplanes, this is the power-off stall speed at the maximum landing weight in the landing configuration (gear and flaps down). The lower limit of the white arc.
Vs1: The stalling speed or the minimum steady flight speed obtained in a specified configuration. For most airplanes, this is the power-off stall speed at the maximum takeoff weight in the clean configuration (gear up, if retractable, and flaps up). The lower limit of the green arc.
Vsr: Reference stall speed.
Vsr1: Reference stall speed in a specific configuration.
Vsro: Reference stall speed in the landing configuration.
Vsw: The speed at which onset of natural or artificial stall warning occurs.
Vx: Best angle-of-climb speed. The airspeed at which an airplane gains the greatest amount of altitude in a given distance. It is used during a short-field takeoff to clear an obstacle.
Vy: Best rate-of-climb speed. This airspeed provides the most altitude gain in a given period of time.
Vyse: Best rate-of-climb speed with one engine inoperative. This airspeed provides the most altitude gain in a given period of time in a light, twin-engine airplane following an engine failure.