A hillclimb race from 1920 to 1957
In English, a hillclimb is not a race. One major difference is that there is never any need for overtaking.
A hillclimb is a competition to cover an ascent against the clock and cars run one at a time.
A race is generally on a closed circuit with a massed start and cars have to overtake to gain position or to lap slower cars. In earlier times some road races also had cars starting one at a time, the Targa Florio, Mille Miglia and the Carrera Panamericana being the best known postwar ones. As the slowest cars started first the faster cars had to overtake them.
Hence my earlier question seeking clarification.