A disaster is a serious problem that happens over a period of time and causes harm to people, things, economies, or the environment that the affected community or society cannot handle it on its own. In theory, natural disasters are those caused by natural hazards, whereas human-made disasters are those caused by human hazards. However, in modern times, the divide between natural, human-made or human-accelerated disasters is more and more difficult to draw. In fact, all disasters can be seen as human-made, due to human failure to introduce appropriate emergency management measures.

(en:Accident)कोणाच्या अन्अवधानाने,नजरचुकीने, यंत्र अथवा यंत्रणेच्या बिघाडाने, मानवी चुकीमुळे,सुरक्षा व वाहतुकीच्या नियमांच्या न पाळण्याने,आळशीपणा,अयोग्य ज्ञान अथवा अज्ञान, खबरदारी अभावी,घडलेल्या घात अथवा आर्थिक नुकसानीस अपघात म्हणतात.अपघात विशिष्ट परिस्थितीजन्य असतात.ते योग्य खबरदारी घेतल्यास टाळता येऊ शकतात. यात जीव व इतर प्रकारचे कमीअधिक नुकसान सहसा समाविष्ट असतेच.