Vowel Duration
Thai vowels are pronounced with either a short or a long duration, and it is important to sustain the correct duration if the
word is to be understood as intended. Our complete
vowels table lists the short-duration vowels on the left columns and the
long-duration vowels in the right columns. You can listen to audio clips there to hear the difference as pronounced by a
native speaker.
Examples follow. Notice that the tone is the same, only the vowel duration differentiates these words:
เขา 
/khao
R/ [3
rd person singular or plural pronoun] he; she; him; her; they; them
ขาว /khaao
R/ [is] white
ไหม /mai
R/ [word added at the end of a statement to indicate a question; "right?"]
หมาย /maai
R/ warrant; notice; order; point; writ; summons; decree
หวัด /wat
L/ common cold
หวาด /waat
L/ [is] startled; frightened; suddenly roused or awakened; apprehensive
คัน /khan
M/ to itch; or feel a need to scratch or sneeze
คาน /khaan
M/ to support; to hold up
As you can see, in these cases we are able to show the long duration vowel in the English-based transcription by doubling-up the vowels. However because vowel
duration isn't really a phonetic feature of English, there are some limitations with this approach. For example, Thai has long- and short-duration
variants of the 'oo' sound, which is already doubled. We use 'oo' for the short-duration and 'uu' for long-duration:
รุ /roo
H/ to evacuate; to purge; to discard
รู้ /ruu
H/ to know a subject or piece of learned information
Whether the vowel in a syllable is long or short is one of the factors that determines the
tone with which the syllable must be spoken.
For more information on this, please see the page on
tone rules.
Finally, please don't be confused by another use of the terms "long vowel" and "short vowel" that you may have encountered:
posted to alt.usage.english 2005 Jan 28 by Bob Cunningham:
Some remarks from different posters in recent days suggest that it's time to discuss again the conflict between two different meanings of “long” and of “short”.
When we were in elementary school, the teacher taught us that the “a” in “rake” was “long a” and the “a” in “rack” was short “a”. And the vowels in “peek”, “pike”, “poke”, “root” were
long while the vowels in “peck”, “pick”, “pock”, and “rut” were
short.
There is another meaning for each of “short vowel” and “long vowel”, and it's the one phoneticians are most likely to have in mind when they use those terms. That is, a
short vowel is one whose
duration is short, and a
long vowel is one whose
duration is long. That is the meaning of “long” and “short” that corresponds to the presence or absence of a colon after a vowel in the
International Phonetic Alphabet.
I've read that there is a connection between the two concepts, in that the vowels that are now referred to by elementary school teachers as “long” and “short” were indeed long or short in duration when the words were applied to them. In modern English, the vowel in “peek” may be pronounced with relatively long duration or relatively short duration, but it's still a high front vowel. And the vowel in “pick“ may be pronounced with either long or short duration, but it's still a near-high, near-front vowel.
In the study of phonetics, the correct terms for the distinction discussed here are
tense vowel and
lax vowel, instead of the misapplied terms “long” and “short,” respectively.
