The letter sequence “ough” occurs frequently in the English language; however, it is the one sequence that has the most number of pronunciations depending, of course, on the word. In American English there are at least six pronunciations; in British English there are over ten.
Here are the six most common American English pronunciations of “ough:”
Bough (rhymes with bow)
Cough (rhymes with coff, as in coffin)
Rough (rhymes with ruff)
Thorough (rhymes with oh)
Though (rhymes with toe)
Thought (rhymes with taut)
Through (rhymes with true)
Additional pronunciations of “ough” include:
Hiccough (rhymes with cup)
Lough (rhymes with lock)
Slough (rhymes with moon, or rhymes with wow)
Interestingly, tough, though, through, and thorough are formed by successively adding one letter; however, none of the words rhyme with one another.
The following sentence contains eight pronunciations: A rough-coated, dough-faced ploughman strode through the streets of Scarborough, coughing and hiccoughing thoughtfully.
The following sentence contains ten different pronunciations: The wind was roughalong the lough as the ploughman fought through the slough and snow, and though he hiccoughed and he coughed, he thought only of his work, determined to be thorough.
English light verse writer and journalist, William Thomas Goodge, wrote “Ough: A Phonetic Fantasy,” featuring the many pronunciations of “ough.”
OUGH: A PHONETIC FANTASY
The baker-man was kneading dough
And whistling softly, sweet and lough.
Yet ever and anon he’d cough
As though his head were coming ough!
“My word!” said he,” but this is rough:
This flour is simply awful stough!”
He punched and thumped it through and through,
As all good bakers dough!
” I’d sooner drive,” said he ” a plough
Than be a baker anyhough!”
Thus spake the baker kneading dough;
But don’t let on I told you sough!
For further reading: http://www.dictionary.com/slideshows/ough#rough