umkommen
to die
To die as a result of an accident, a disaster, a war, or a crime; to lose one's life.
Bei dem schweren Erdbeben sind leider Hunderte von Menschen umgekommen.
Sadly, hundreds of people died in the severe earthquake.

to die / to spoil
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to die
To die as a result of an accident, a disaster, a war, or a crime; to lose one's life.
Bei dem schweren Erdbeben sind leider Hunderte von Menschen umgekommen.
Sadly, hundreds of people died in the severe earthquake.

Since 'umkommen' (to die) describes a change of state (from life to death), the perfect tense is always formed with the auxiliary verb 'sein' (to be), not with 'haben' (to have). This is a common mistake.
Bei dem Flugzeugabsturz sind alle Passagiere umgekommen.
All the passengers died in the plane crash.
'Umkommen' (to die) is a separable verb. In a main clause in the present or simple past tense, the prefix 'um-' comes at the end of the sentence.
Jedes Jahr kommen viele Menschen bei Verkehrsunfällen um.
Every year, many people die in traffic accidents.
To name the cause of death, the prepositions 'bei' (in/during) for an event (e.g., an accident, a fire) or 'durch' (through/from) for a direct cause (e.g., an explosion, an illness) are often used.
Er ist bei einem Lawinenunglück in den Alpen umgekommen.
He died in an avalanche accident in the Alps.
The meaning 'verderben' (to spoil) for food is very rare today and is perceived as outdated. You find it almost only in old literature or regional dialects.
Lass das Gemüse nicht in der Sonne liegen, sonst kommt es um.
Don't leave the vegetables lying in the sun, or they will spoil.
to fall
'fallen' and 'umkommen' can both mean that someone dies because of a terrible event. 'fallen' is used especially for people who are killed in a war or battle. It often sounds official or historical. 'umkommen' is broader: people can die in an accident, a disaster, a crime, or also in a war. For normal deaths without such danger, neither word fits very well. So the difference is mainly the context: battle and war for 'fallen', a dangerous event in general for 'umkommen'.

Bei dem schweren Sturm kamen mehrere Menschen um.
Several people died in the severe storm.
Der junge Soldat fiel im Krieg weit weg von seiner Heimat.
The young soldier fell in the war, far from his homeland.