“Do not force nouns or other parts of speech to act as verbs,” says The Economist Style Guide; while in Lost for Words, Humphrys writes similarly that “verbs can refresh a sentence any time they are needed – but not if they earned their crust as nouns in an earlier life.” This goes beyond mere lexical Nimbyism: “wordclass conversion” is absolutely vital to English. Take cloud. In the ninth century it was a noun meaning a pile of rocks or a hill (cloud is related to clod and clot). Around 1300, clouds became (as they still are) heaps in the sky. Then in the 16th century, cloud was converted into a verb, meaning to “darken” or “obscure”. Catastrophe? No: good news. Gripers rate the expression epic fail to be an example of what it names, decrying this use of fail as a noun on the grounds that fail is, and should only be, a verb. Yet in the expression without fail, they accept the noun fail exactly as the phrase describes.