Short And Long Vowels

Vowel length is phonemic in Thai: a short vowel and its long counterpart can distinguish words. Learn the vowel’s length and its tone as separate parts of the word’s sound pattern.

1. Short And Long Vowels
The contrast concerns vowel duration. A short vowel is brief; its long counterpart is held longer in the contrast being practised. “Short” and “long” are categories, not a requirement that every long vowel last exactly twice as long. In the standard citation readings shown here, a short vowel with no written final consonant ends with a glottal stop. กะ has short a; กา has long aa. These two words also differ in tone.

2. Length And Tone Rules
Syllables ending in p, t, or k sounds, and short-vowel syllables ending in a glottal stop, are dead syllables. For a low-class initial with no tone mark, a dead syllable with a short vowel has a high tone, while one with a long vowel has a falling tone. This gives คัด a high tone and คาด a falling tone. With no tone mark, dead syllables with mid- or high-class initials have a low tone whether the vowel is short or long. Length alone does not determine every syllable’s tone.

3. Writing The Contrast
The Thai script represents length through different vowel spellings. The short a written -ะ without a final consonant is written ◌ั when a final consonant follows, as in กัด. In เป็ด, the mai tai khu mark (◌็) is part of the spelling of the short vowel. It is not a tone mark; consonant class and the syllable ending still matter for tone.

4. Practise Length And Tone Together
Keep กะ short and กา long when comparing them. กะ also has a low tone, while กา has a mid tone. Do not use a change in pitch in place of a change in vowel duration. Use the spelling, length, and tone rules together when learning a word.