The main Pronunciations of <o> in a stressed syllable :

/a/ as in the word "hot

/ə/ as in the word "come"

/ɔ/ as in the word "dog"

/ʊ/  as in the word "cold"

How do I know when to use the right vowel when I see <o> in a word?

Here's where it it gets tough because unfortunately there really isn't a rule which works consistently for determining the pronunciation of <o>. But...

General rule: When you see a single letter <o> in a stressed syllable of a word,<o> will be pronounced /a/, as in "hot", "god" or "dollar". This is true about 75% of the time.

You may be wondering, how can I recognize all the exceptions- all the other words which are not pronounced /a/ but are pronounced /ə /, /ɔ / or /oʊ /.

The importance of memorization

The answer to that is memorization- that's right- word by word memorization .

Unfortunately, sometimes, this is the best we can do in English. Sometimes in English, you can't sound out a word letter by letter. You just have to remember it like was a picture and associate a sound with that picture.

In general, you can assume that a single letter <o> will be /a/ . However, there are many exceptions to this.

That's why I always recommend to my private students in New York that they begin making a chart which categhorizes words that are spelled with <o> according to their vowel sound.

Here's how the chart looks:

Pronunciation of the letter <o>

/a/                /ə /             /ɔ/              /oʊ /     

hot              come         dog           cold

dollar         Monday       boss         most

It's not only about the long and "fancy" words

Every time you find a word spelled with a single letter<o> in a stressed syllable, categorize it under its approriate vowel sound.
This may seem like a lot of work but actually, even though there are thousands or words which have <o> in a stressed syllable, there are really only a few hundred that we actually uses on a day to day basis.
If you can master the pronunciation of the words that we use most frequently, all the time, you'll greatly change your accent because those are the words people will hear most of the time.

One of the most important parts of accent reduction is learning the simple but important words that we use everyday, every hour, every minute. Pronouncing those words correctly will make the most noticeable difference in your accent.

So lets' begin filling out our chart and begin categorizing some imporatant words which are spelled with a single letter <o> on a stressed syllable. 

Please listen and repeat the following words.

Pronunciation of the letter <o>

/a/                 /ə /                  /ɔ/                     /oʊ /     

lock             monday        dog                most

stop            come             cost               cold

problem     mother         office              won't

dollar          money          boss            owner

Now it's up to you to continue filling in this chart. Try thinking of as many words as possible which contain <o> on a stressed syllable .
Remember, chances are the pronunciation is one of four posibilities /a /, /ə /, / ɔ /or /oʊ / . try putting the word in the correct column.

You can use a dictionary to check see that you've categorized the word correctly. Dictionaries always contain a phonetic transcription.
Keep adding words to your chart everyday. The more words you categorize according to their vowel sound, the more accurate your pronunciation will become.

Improving your accent is a gradual process; nobody can do it overnight.
But learning to speak English clearly and correctly is possible!
With the right amount of work, dedication and training you will reach your goals!

You need the right tools!

It's important to have the right training tools for learning English pronunciation.
That's why I recommend  Best Accent Training mp3s!

Download  Best Accent Training mp3s onto your mp3 player. Take it with you and practice wherever you go!

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Thank you and see you next time!