These words refer to misfortunes that result in grave loss or heavy casualties. Catastrophe is equally appropriate for a personal or public misfortune: taking along a first-aid kit to cope with unexpected catastrophe ; air pollution that has reached the proportions of a catastrophe . In personal application, the word is often used hyperbolically of minor incidents: how to deal with the catastrophe of a large, visible run in her stocking. In reference to a general event, the word may refer to the negative effect on a particular group rather than to the public as a whole: a land reform programme that benefited the poor but was a catastrophe for rich landowners. Cataclysm is most sharply in contrast with these possibilities of catastrophe in allowing little use for personal misfortune and in restricting itself to severe mishaps that have negative results for everyone; it stresses, furthermore, a momentous disruption that results in severe damage and loss: a hairbreadth escape from nuclear cataclysm . More than these other words, cataclysm is especially suggestive of a natural upheaval: the extinct volcano’s eruption would mean a cataclysm for the city.

Disaster is the most general of these words, referring both to personal and public misfortunes in a wide range of possibilities: household disasters ; a country afflicted with the twin disasters of food shortages and an exploding population. Like cataclysm , the word can refer to natural upheavals, but without the implications of total destruction present in cataclysm : a flood that was the worst disaster the city had ever faced. Disaster compares with catastrophe by stressing the actual harm done: They were glad they had survived the catastrophe and had met with no disaster . The word can, of course, be used hyperbolically, like catastrophe , for minor misfortunes: a party that turned out to be a complete disaster .

Calamity is similar to catastrophe , but at a reduced level of intensity. It may also now sound more formal than these other words, or at least shade outdated. It is more often used for a personal misfortune, seriously or hyperbolically, but it can also be used of public misfortunes on occasion, in which case it functions more abstractly or subjectively than disaster : a little calamity that happened on his way to school; a calamity that wiped out his savings; arguing that the bill’s passage would result in a calamity for the whole country. Debacle once referred specifically to a serious disruption or natural upheaval, as of a flood, especially when severe damage or failure results: the debacle of the Children’s Crusade; a stock-market debacle . Now, the word more often refers to an attempt that is ridiculously inept or that results in humiliating defeat: a high-level conference that was nothing short of a debacle .