I'm always confused about how to pronounce words with letter o in spelling. For example, in the word boss, I always pronounce the o as short o, when in fact it is long o. Collar is short, but I always pronounce it the opposite way.

What's the difference between words like dog, top, caught and cost? /ɑ/ or /ɔ/ ?

Are there any rules or law to decide whether to pronounce long o or short o?

  • 3
    There's some potential for confusion here because English phonetics often use long to describe vowel tenseness (like the O in hose) rather than duration (like the O in boss). Jan 17, 2014 at 19:42
  • 1
    The most important thing is that “long” and “short” don’t make much sense, as they are used in different ways by different people. As to which sound you get, it all depends on just which types of mergers or splitters the people you’re talking about talking are part of. Remember that the letter a also takes on the value from thought in words like call for most speakers. There is also something going on in parts of California where even more roundedness is being lost than normal. See here.
    – tchrist
    Jan 17, 2014 at 21:11

2 Answers 2


See the lot-cloth split section of Wikipedia. Here are two excerpts:

The lengthening and raising generally happened before the fricatives /f/, /θ/ and /s/. In American English the raising was extended to the environment before /ŋ/ and /ɡ/, and in a few words before /k/ as well, giving pronunciations like /lɔŋ/ for long, /dɔɡ/ for dog, and /tʃɔklɨt/ for chocolate.

The sound change is most consistent in the last syllable of a word, and much less so elsewhere. Some words that entered the language later, especially when used more in writing than speech, are exempt from the lengthening, e.g. joss and Goth with the short vowel.

Translating from IPA for those people who don't know it, the vowel is generally long before the sounds 'f', 's', 'th', 'g', 'ng', 'nk', especially in one-syllable words. There are exceptions both ways. For example, it's usually short in cog and long in chocolate. I don't believe there's any way to figure out which words are the exceptions.

  • Thanks. And words like top, dog, caught, cost, are they pronounced as /ɑ/ or /ɔ/ if disregard long or short?
    – yysur
    Jan 17, 2014 at 17:08
  • 1
    Unless it's a very unusual dialect, all long 'o's are pronounced with /ɔ/ and all short ones with /ɑ/. The original British short 'o' only split into two sounds in American. Jan 17, 2014 at 17:10
  • Actually, let me make an addendum to my last comment. All long 'o's will be pronounced the same, and all short 'o's will be pronounced the same. In dialects with the Northern Cities Shift, these aren't exactly the IPA vowels /ɔ/ and /ɑ/. Jan 17, 2014 at 21:58
  • I'm curious; how do you pronounce the letter "o"? Would you be willing to visit here, select vowels/monopthongs/back, and hear /o/, and tell me if that is the long o sound? Jan 18, 2014 at 1:13
  • What the OP is asking about (from his examples of dog, top, caught and cost) is the difference between the British short o sounds /ɒ/ which in American have become /ɔ/, as in dog, moth, caught, cost, coffee and chocolate (called "long o" in the question), and those British short o sounds which in American have become /ɑ/, as in cog, cot, cop (called "short o" in the question). The /o/ on that website is not the "long o" sound the OP is talking about; he's taking about /ɔ/. Jan 18, 2014 at 4:41

I pronounce "boss" and "collar" the same, just as I say "father". I'm from the US.

  • dog, boss, collar, caught, and cost all use the same sound to my ear.
    – Doc
    Jan 17, 2014 at 19:16
  • There's a difference in vowel duration, which is usually called length in phonetics. Unfortunately, English language teachers typically use length to describe a completely different quality. Jan 17, 2014 at 19:44

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