In many sport

Sport

A Sport is all forms of physical activity which, through casual or organised participation, aim to use, maintain or improve physical fitness and provide entertainment to participants. Sport may be competitive, where a winner or winners can be identified by objective means, and may require a degree...

s, a competition number is used to identify and differentiate the competitors taking part in the competitive endeavour. For example, runners in a race will wear a prominent competition number so that they may be clearly identified from a distance.

Vehicles

In motorsport

Motorsport

Motorsport or motorsports is the group of sports which primarily involve the use of motorized vehicles, whether for racing or non-racing competition...

, competition numbers are attached to the vehicles taking part, also for identification. In some types of motorsport such as rallies

Rallying

Rallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...

, the competition number works in conjunction with special kinds of timing system (for example targa timing

Targa timing

Targa timing is a system of timing used in car rallying. It was invented by John Brown, the Clerk of the Course for the Targa Rusticana, a road rally that used to be run in the United Kingdom in the 1960s by Oumdc...

) and as a result numbers also usually relate to the competitors' due time

Due time

In rallying, a competitors' due time is simply the time that they are due at the next time control. If the crew arrive on or before their due time, they will incur no time penalty...

and thus may exhibit gaps such as skipping from number 59 to number 100 (59 minutes to 1 hour due time).