Efficiency.
You could very well have one contained area to run every running and field event in Track and Field but than it would take a considerable amount of time and organization to host every event in such a limited compartment. Having separate (devoted) areas for only a small number of events relinquishes the main track for only the track events and it's participants to compete in.
Other added benefits could include compartmental wear and tear to a specific areas, much more warm-up and preliminary time and trials to suit the participants, additional lanes on a track can bolster competitiveness as well.
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Track and fields
Some of them are Athletics, swimming, diving, shooting, show jumping , football etc..
,Races, long jump,high jump, javelin throw, disc throw, shot put, relays
Track Events.
There are many Olympic events, here are four:- Athletics, Rowing, Boxing, Swimming.
a stadium
You can calculate the probability of the outcome of events.
Did you mean "heptathlon"? A heptathlon is a track and field athletics combined events contest made up of seven events.
Judo Archery Trampoline Athletics
Events in the 1896 Games were in athletics, wrestling, cycling, gymnastics, fencing, weightlifting, tennis, swimming, and shooting.
There is track and field events, but athletics covers all sports, because, all sports people consider themselves athletes