American English dictionaries show that thought contains the vowel /ɔ/ while lot contains /ɑ/. They’re presented as two separate sounds, and for some Americans that’s absolutely true. But you might be surprised to discover that millions of Americans don’t make that distinction anymore.
In fact, I’m one of those people! In my version of Standard American (SA), I pronounce thought and lot with the exact same syllable: /ɑ/, and I rarely teach /ɔ/ to my accent modification students anymore.
What happened to /ɔ/, and why do so many Americans not even have it in their personal sound set?
Meet the Cot–Caught Merger
What happened is this: across most of the United States, the vowels in words like cot and caught have merged into a single sound. Linguists call this the cot–caught merger, and it is one of the biggest pronunciation changes in contemporary American English.
For speakers with the merger, all of these pairs sound identical:
- cot – caught
- Don – dawn
- stock – stalk
- caller – collar
- knot – naught
Today, the merger dominates much of the Western United States, the Midwest, and large parts of the South. Only certain regions, such as parts of the Northeast and a few other areas, consistently maintain two separate vowels.
In other words, if you’re aiming for a broadly General American accent, producing two different vowels may actually make you sound less American.
What Does the Merged Vowel Feel Like?
The merged vowel is basically the /ɑ/ sound, which we covered in depth in a separate post, and is produced with:
- a comfortably low jaw
- the tongue low and toward the back of the mouth
- no lip rounding
This is the stressed vowel found, for example, in the words father, palm, and spa.
The /ɔ/ vowel, as in thought, all, or walk, is pronounced with rounded lips, similar to the British pronunciation. There’s nothing wrong with continuing to use the /ɔ/ in these words. In fact, maintaining the distinction is perfectly natural in many parts of the United States.
But if you’re learning a more general form of American English for work, university, or everyday life in the United States, the merged vowel is often the more natural choice.
Why Is the Merger Happening—and Is It Still Spreading?
The cot–caught merger is happening for a simple reason: languages tend to simplify contrasts when speakers no longer need them to distinguish meaning.
In this case, English once maintained two separate low-back vowels in many dialects. Over time, however, the difference between them became less important in everyday speech for many communities, and the two sounds gradually moved closer together until they became one.
Several forces helped this happen:
- Natural sound change: vowels shift over generations, and small changes can eventually erase a contrast.
- Dialect leveling: as people move, mix, and interact more widely, regional differences often become less distinct.
- Language acquisition: children usually adopt the vowel system they hear around them, so once a merger becomes common in a region, it tends to stay stable.
- Reduced functional load: English has many other ways to distinguish words, so losing this one contrast usually does not cause confusion.
Is the merger still occurring? In some places, yes.
In much of the West and Midwest, where I spent my childhood, the merger is already well established and has been for decades. In those regions, it is no longer a new change so much as the normal local pattern.
In other parts of the country, especially some areas of the Northeast and a few other places, the merger is still incomplete or uneven. Younger speakers in some traditionally unmerged regions may be moving toward the merged system, while older speakers may still preserve the distinction.
A Simple Exercise to Practice Changing From /ɔ/ to /ɑ/
If you are pronouncing the /ɔ/ and want to replace that sound with a more general /ɑ/, start by saying these words:
- thought
- all
- walk
- call
- fall
- talk
- bought
Now imagine you’re saying the vowel in father.
As you pronounce each word:
- Let your jaw drop comfortably.
- Keep your tongue low and slightly back.
- Relax your lips instead of rounding them.
Record yourself, then compare your pronunciation with speakers from states like California, Ohio, Washington, Colorado, or Oregon. You’ll notice that their thought vowel is remarkably open and unrounded.
Both Versions Are Correct, But /ɑ/ Is Now the More “Standard” Version
In brief, the merger to the /ɑ/ vowel is very widespread, but there are still parts of the United States that retain the rounded vowel /ɔ/ in words like thought.
Ultimately, the accent you want to sound like should determine whether you need to pronounce the /ɔ/ sound. So the advice that I generally give to my students is this: unless you live in the Northeastern part of the U.S. or another area where the /ɔ/ is still retained, drop /ɔ/ completely from your sound set, as you probably don’t need it!
