Angle of climb
In aerodynamics, climb gradient is the ratio between distance travelled over the ground and altitude gained, and is expressed as a percentage. The angle of climb can be defined as the angle between a horizontal plane representing the Earth's surface and the actual flight path followed by the aircraft during its ascent. The speed of an aircraft type at which the angle of climb is largest is called V. It is always slower than V, the speed for the best rate of climb. As the latter gives the quickest way for gaining altitude levels, regardless of  the distance covered during such a maneuver, it is more relevant to cruising. The maximum angle of climb on the other hand is where the aircraft gains the most altitude in a given distance, regardless of the time needed for the maneuver. This is important for clearing an obstacle, and therefore is the speed a pilot uses when executing a "short field" takeoff. V increases with altitude and V decreases with altitude until they converge at the airplane's absolute ceiling.