Here’s a little exercise: which of the words in the following sentence do you think need a diacritic (or some sort of accent), and which don’t?
“Chloe and Rene are cooperating: she’s reading his expose and he’s proofing her resume in a cafe where they’re eating pate as an appetizer, chicken mole as an entree, and souffle for dessert, all washed down with some rose, sake, frappe, and a soupcon of naive romance.”
As we can see from this sentence, there are a few English words — such as rosé, exposé, resumé, and saké — that can be more easily distinguished in meaning from their non-accented homographs (in this case the nouns rose and sake and the verbs expose and resume) by donning a diacritic; others don’t need the linguistic leg-up to be understood. As well as clarifying meaning, accents can serve another helpful purpose: to indicate pronunciation (e.g. frappé, naïve, soufflé).
English, unlike most other European languages, doesn’t have many words that contain diacritics, unless they have been adopted from other languages — especially French — and haven’t been fully assimilated into the vocabulary. However, there are a few exceptions: loanwords that appear in English more frequently with their native diacritics than not are café, cliché, and passé; also, curiously, those associated with food and cookery are less likely to lose their accents (eg. soupçon, soufflé and entrée). Words that have long been in the English vocabulary, even if originally imported from other parts of the world, tend to lose their foreign accessories eventually: hence facade, elite, decor, role and debut. The Associated Press, like most important style guides, ignores all accents. The Economist offers a sensible but ambiguous prescription, allowing for pronunciation accents that are considered ‘crucial’ and advocating accents ‘on French words’ (but who is to determine what is crucial and what is still French?):
“On words now accepted as English, use accents only when they make a crucial difference to pronunciation: cliché, soupçon, façade, café, communiqué, exposé (but chateau, decor, elite, feted, naive). If you use one accent (except the tilde—strictly, a diacritical sign), use all: émigré, mêlée, protégé, résumé. Put the accents and cedillas on French names and words, umlauts on German ones, accents and tildes on Spanish ones, and accents, cedillas and tildes on Portuguese ones: Françoise de Panafieu, Wolfgang Schäuble, Federico Peña, José Manuel Barroso. Leave accents and diacritical marks off other foreign names. Any foreign word in italics should, however, be given its proper accents.”
A number of words dress up or down — with or without their accents — according to personal and house style; examples are resumé, saké, naïve, élan, and séance. Proper names such as Renée, Zoë and Chloë* tend to retain rather than omit their original diacritical marks, arguably for their color as much as to encourage their correct pronunciation. The reality star Khloé Kardashian changed her first name from Khlóe to Khloé. Go figure.
Some old-fashioned (and dare I say slightly pretentious) writers prefer to retain accents that the rest of the English-speaking world have long since allowed to fall by the wayside: you’ll occasionally see élite, rôle, début and even hôtel in especially pompous prose. The diaeresis (similar to the German umlaut, and used to indicate neighboring vowels that shouldn’t be mixed but are pronounced separately) also falls into this old-fashioned category — naïve being a fairly common but singular exception (along with the girls’ names mentioned above). Words such as coöperate, reëstablish, and noöne now have modern spellings, often using a hyphen to separate offending vowel pairs: the OED lists them respectively as cooperate or co-operate, re-establish, and no one (two separate words). However, the New Yorker magazine, presumably staying true to its nearly 90-year-old style guide, still uses the diaeresis with consistency and pride.
* Chloe is the name of a 1927 jazz standard written by Charles N. Daniels and Gus Kahn; a 2009 movie starring Julianne Moore, Liam Neeson and Amanda Seyfried; a hurricane (0f 1967); and a tropical storm (1971). Chloé is a French fashion house founded in 1952, and a 1875 painting by Jules Lefebvre. 402 Chloë is a large main-belt asteroid named after the goddess.