One of the biggest problems with the alphabet is that English has more vowels than A E I O U. The aw-sound is one of the others. It is a vowel sound and one must round the lips to pronounce it properly. There was no letter in the Roman alphabet for this sound when English started using the alphabet. So two letters are used together as a digraph to represent one sound. The aw-sound is not a blend of 'a' and 'u' or 'uu' (w).
Another problem with the aw-sound is that native English speakers from different places pronounce it differently as a short or long sound. The IPA symbol may be followed by a colon to indicate it is a long vowel sound or without a colon if it is short. In a few local varieties, particularly in some parts of the US, this sound has been reduced to a short o or a schwa-sound in many words. So not every example I give works in every local English variety.
The aw-sound is spelt several different ways. The most common are aw, au and al as in law, daughter, and walk respectively. However it is also spelt a, o, augh, ough, as in wash, or, naughty and ought. (Different English varieties use either a short o sound or an aw-sound for wash.)
When the aw-sound is found at the beginning of a word the au- spelling is most commonly used. (The exception is the word ought, which comes from Old English.) Those aw-sound words spelt au- usually come from French or Latin, unless spelt augh. Examples: author, audit and auction. Except for this paragraph, all the examples used in this article are words descended from Old English.
Since both u and w had a similar sound in Middle English, they both appear as the second character in digraphs, for example au/aw, eu/ew and ou/ow. In Middle English there were no strict spelling rules; the letters u and w were used interchangeably. However Modern English usually uses au(gh) internally and aw at the end of the word. There are, of course, exceptions to this pattern, such as dawn. That leads to another spelling pattern, the aw spelling can be in the middle of a word if it is immediately before a single L, K or N. Examples include: sprawl, hawk and drawn.
The aw-sound is an important English vowel. The spelling patterns here are useful, but too complicated to be memorised by rote. Be warned that native English speakers' pronunciation of this vowel varies a lot. Although less common than the short/long A E I O and U, the aw-vowel sound is an important part of English and found in many common words.
by John Larrysson
A native English speaker who has been teaching practical English in Hong Kong for more than a decade.