Ough is a four-letter sequence, a tetragraph, used in English orthography and notorious for its unpredictable pronunciation. It has at least eight pronunciations in North American English and nine in British English, and no discernible patterns exist for choosing among them.
In Middle English, ough was regularly pronounced with a back rounded vowel and a velar fricative (e.g., [oːx], [oːɣ], [uːx] or [uːɣ]).
|/ʌf/||Brough, chough, enough, Hough, rough, slough (see below), sough, tough||Rhymes with puff, stuff. Sough is also pronounced /saʊ/.|
|/ɒf/||cough, Gough, trough||Rhymes with off, scoff. Trough is pronounced /trɔːθ/ (troth) by some speakers of American English, and a baker's trough is also pronounced /troʊ/.|
|/aʊ/||bough, doughty, drought, plough, slough (see below), Slough, sough||Rhymes with cow, how. Sough is also pronounced /sʌf/.|
|/oʊ/||although, dough, furlough, though||Rhymes with no, toe.|
|/ɔː/||bought, brought, dreadnought, fought, nought, ought, sought, thought, wrought||Rhymes with caught, taught. Regularly so used before /t/, except in drought /draʊt/ and doughty /ˈdaʊti/. In dialects exhibiting the cot-caught merger, this is realized as /ɒ/ or /ɑː/.|
|/uː/||brougham, slough (see below), through||Rhymes with true, woo.|
|/ə/||borough, Poughkeepsie, thorough, Willoughby||Pronounced /oʊ/ in American English, thus rhyming with burrow and furrow, except when reduced by a following syllable in many dialects, as in Poughkeepsie, thoroughly or Willoughby.|
|/ʌp/, /əp/||hiccough||Variant spelling of the more common hiccup.|
|/əf/||Greenough||Pronounced /ˈɡrɛnəf/ as the name of a river in Western Australia. As a surname, usually pronounced /ˈɡriːnoʊ/, like although and dough.|
|/ɒk/||Clough, hough, lough, turlough||Rhymes with cock, lock. Hough more commonly spelled hock from the 20th century onwards. Lough (an Irish cognate of Scots loch) and turlough are also pronounced /lɒx/.|
|/ɒx/||lough, turlough||Rhymes with Scots loch. Lough and turlough are also pronounced /lɒk/.|
Slough has three pronunciations, depending on its meaning:
The town of Slough in the Thames Valley of England is /slaʊ/.
An example sentence using the nine pronunciations commonly found in modern usage (and excluding hough, which is now a rarely used spelling) is, "The wind was rough along the lough as the ploughman fought through the snow, and though he hiccoughed and coughed, his work was thorough."
Another, slightly shorter example would be, "The rough, dough-faced ploughman fought through the borough to the lough, hiccoughing and coughing."
Other pronunciations can be found in proper nouns, many of which are of Celtic origin (Irish, Scottish or Welsh) rather than English. For example, ough can represent /ɒk/ in the surname Coughlin, /juː/ in Ayscough, and /i/ in the name Colcolough (/ˈkoʊkli/) in the United States.
The two occurrences of ⟨ough⟩ in the English place name Loughborough are pronounced differently, resulting in /ˈlʌfbərə/. Additionally, three parishes of Milton Keynes—Woughton /ˈwʊftən/, Loughton /ˈlaʊtən/ and Broughton /ˈbrɔːtən/—all have different pronunciations of the combination.
Tough, though, through and thorough are formed by adding another letter each time, yet none of them rhyme in British English (in American English, however, though and thorough do rhyme).
Some humorous verses have been written to illustrate this seeming incongruity:
Because of the unpredictability of the combination, many English spelling reformers have proposed replacing it with more phonetic combinations, some of which have caught on in varying degrees of formal and informal success. Generally, spelling reforms have been more widely accepted in the United States and less so in other English-speaking areas. One problem is that a pronunciation with the velar fricative is still found locally in parts of North-East Scotland, where, for example, trough is pronounced /trɔːx/.
In April 1984, at its yearly meeting, the Simplified Spelling Society adopted the following reform as its house style: