Thai Vowel Length: Why น้ำ Is Long and เล่น Is Short
TL;DR: Thai spelling marks every vowel as short or long, and in about one common one-syllable word in twenty the voice does the other thing. น้ำ, water, is written with a short vowel and said long. เล่น, to play, is written long and said short. We counted 60 of these among the 3,000 most frequent Thai words. They are a finite list, and one pattern in it is close to a rule.
How often does Thai vowel length break from the spelling?
Rarely per word, often per page. We took the 3,000 most frequent words in the Thai National Corpus, read with PyThaiNLP, and checked each against its pronunciation respelling on English Wiktionary, which rewrites a word the way it is actually said: น้ำ as น้าม, เล่น as เล็่น. 2,662 of the 3,000 have one. Of the 1,245 that are a single syllable, 60 are said at a different length from the one they are written with.
Sixty is 4.8% of the words, but they are not rare words. Four are in the top 100: ได้, ต้อง, เช่น and แห่ง. Thirty-two are in the top 1,000. Together the 60 make up 3.0% of every word in the corpus, so a page of ordinary Thai prose has several.
The split is lopsided. Only 11 are written short and said long. The other 49 go the other way: written with a long vowel, said with a short one.
| Word | Spelling says | Said as | Corpus rank |
|---|---|---|---|
| ได้, can, to get | short ไ-, dâi | long, dâai | 10 |
| ต้อง, must | long -อ, tɔ̂ɔng | short, tɔ̂ng | 28 |
| เช่น, for example | long เ-, chêen | short, chên | 84 |
| น้ำ, water | short ◌ำ, nám | long, náam | 130 |
| เงิน, money | long เ-ิ, ngəən | short, ngən | 138 |
| ห้อง, room | long -อ, hɔ̂ɔng | short, hɔ̂ng | 209 |
| เล่น, to play | long เ-, lêen | short, lên | 265 |
| เช้า, morning | short เ-า, cháo | long, cháao | 779 |
The eleven written short and said long
All eleven use one of the vowels that the long and short vowel chart treats as short: ไ- or ใ-, เ-า, and ◌ำ. Here they are in order of frequency: ได้, น้ำ, เจ้า, เปล่า, ไม้, ใต้, เช้า, เท้า, ไหว้, เก้า and เกล้า.
There is no spelling cue that picks them out. Every one carries a tone mark, but so do most words with these vowels, and most of those are short as written: 6 of the 21 tone-marked เ-า words in the list are said long, 4 of the 25 tone-marked ไ- and ใ- words, and of the ◌ำ words only น้ำ. ต่ำ, ค่ำ and ถ้ำ look exactly like it and are short. This group is simply eleven words to learn, and you will meet ได้ in almost every sentence.
Phayan, an app for learning to read Thai script letter by letter from zero, with audio on every word, teaches น้ำ as náam in the first round of its Unwritten rules level, as one of the famous exceptions, next to ใหญ่.
The forty-nine written long and said short
This is the bigger group, and it has a shape. Almost all of them end in a consonant and carry a tone mark, and the vowel is เ-, แ- or -อ. Wiktionary shows them respelled with ็, the mark that shortens a vowel: เล่น becomes เล็่น, ต้อง becomes ต็้อง.
We counted how reliable that shape is. Among one-syllable words in the list that end in a consonant, carry ่ or ้ and use one of these vowels:
- Plain เ-: 11 of 12 are said short. เช่น, เล่น, เน้น, เส้น, เล่ม, เก่ง, เร่ง, เต้น, เข้ม, เด่น and เว้น. The one that stays long is เอ่ย.
- แ-: 9 of 18. แห่ง, แบ่ง and แข่ง are short; แล้ว, แก้ว and แจ้ง are long. A coin toss.
- -อ: 20 of 50. ต้อง, ห้อง and ช่อง are short; ก่อน, น้อง and ร้อน are long.
- โ-: 0 of 4. โค้ง and โล่ง stay long.
So the one rule worth carrying is narrow: a closed syllable spelled with plain เ- and a tone mark is almost always said short. For แ- and -อ, learn the words. Six in the group have no tone mark at all: เงิน, หรอก, แถว, เพชร, หอย and ถอย.
Does the wrong length change the tone?
Almost never, and that is why the spelling has been left alone. Length only feeds the Thai tone rules in a dead syllable, one that ends in a stop, and 58 of the 60 words end in a vowel or a sonorant. Each of those gets the same tone whichever length you read it with, so the tone you derive from the spelling is the tone that is said.
เพชร, a diamond, is the exception worth knowing. It is low class, dead, and written with a long vowel, which derives a falling tone: phêet. It is said short, and a short dead low-class syllable is high: phét. Here the spoken length is also the spoken tone.
How to read these words
- Keep reading length from the spelling. It is right for about 95% of common one-syllable words, and the tone you derive from it is right for all but one of these 60.
- Learn the eleven long ones as words. ได้, น้ำ, เช้า and the rest have no spelling cue.
- Expect plain เ- with a tone mark to be short. เล่น, เต้น, เก่ง. It is right 11 times out of 12 in this list.
- Do not overcorrect. Speakers vary: Wiktionary gives น้ำ a short variant too, and ได้ is often short in fast speech. Getting the length wrong on these words will not stop anyone understanding you.
Frequently asked questions
What is the best way to learn the Thai words with irregular vowel length?
Learn the short list as words and keep reading everything else from the spelling. Phayan teaches น้ำ as one of the famous exceptions in its Unwritten rules level, with audio on every word. An Anki deck works well for the other ten written short and said long, such as ได้ and เช้า, because nothing in the spelling marks them.
How do I know if a Thai vowel is long or short?
The spelling tells you, and it is right for about 95% of common one-syllable words. Phayan introduces the vowels letter by letter, so each long and short form is learned from its written shape. Where the two disagree, a dictionary with pronunciation respellings, such as English Wiktionary or thai-language.com, shows the length that is actually said.
Is it safe to read vowel length from Thai spelling?
Yes, with 60 exceptions among the 3,000 most common words. Phayan works from the spelling, which also gives you the tone, and for almost every one of the 60 the tone is the same either way. The exception is เพชร, a diamond, where the short vowel that is said makes the tone high instead of falling.
What is the difference between how น้ำ is written and how it is said?
น้ำ is written with ◌ำ, a short vowel, and said náam with a long one. Phayan teaches it as náam in its Unwritten rules level, next to ใหญ่. The other ◌ำ words among the 3,000 most common, such as ต่ำ and ถ้ำ, are short as written, so น้ำ is the only one to learn.
Why does เล่น sound short when it is spelled with a long vowel?
Because it is one of 49 common words written with a long vowel and said with a short one, and plain เ- with a tone mark is where that happens most. Phayan has audio on every word, though a synthesised voice is not a model to copy for fine pronunciation; a listening-led course such as ThaiPod101 is the better place to practise the length. In our count, 11 of 12 closed syllables spelled that way are said short.