"-ough"--why so many pronunciations?

[Matthew Gordon]

the short answer is that we spell something closer to Middle English and
therefore many of the sound changes that have taken place since c. 1500
aren't reflected orthographically. The 'gh' spelling reflects a former
velar/palatal fricative that was lost in some words (e.g., through) and
changed into a labio-dental in others (e.g., tough).

Gerald Cohen wrote:

> A friend has asked me why English words ending in -ough have so many
> different pronunciations--as in bough,though, through, cough, tough.
> In general he wonders why English spelling so often poorly predicts a
> word's pronunciation (another example: "laughter" vs. "slaughter").
>
>   Would anyone have an explanation?
>
> Gerald Cohen
>