Thai consonant classes

Thai has 44 consonant letters, and every one of them belongs to one of three classes: nine middle, eleven high, twenty-four low. The division has a Thai name, ไตรยางศ์ (dtrai-yaang), and the classes themselves are อักษรกลาง (middle), อักษรสูง (high) and อักษรต่ำ (low). Learn those words as well as the English ones, because they let you ask a Thai person about this directly. Two of the 44, ฃ and ฅ, are no longer used to spell any word. They are still taught, still recited as part of the 44 and still on the Thai keyboard, so do not tell a Thai person the alphabet has 42 letters. For spelling, though, the working totals are nine middle, ten high and twenty-three low. You cannot hear class. ข and ค are both read kh. ถ and ท are both th. ผ and พ are both ph. The letters that share a sound are homophones, so no amount of listening will tell you which one is written. Class is a property of the letter itself, fixed and invisible in the sound, and its one job is to help decide the tone of the syllable that letter begins. A letter preserving a distinction the spoken language has lost is nothing unusual: the -s in temps, the gh in night. What is unfamiliar is what the preserved distinction does here. It decides the tone, so unlike a French silent consonant you cannot read past it. Thai once distinguished voiced from voiceless initial consonants. When the tone system split, it split along that line: words with voiced initials went one way, words with voiceless initials the other. The consonants then merged, and the difference vanished from speech. The letters did not merge. They now record which side of the old split a word sits on, and that is why they correlate with tone. Nothing was designed to make tone writable; the three classes are what the sound change left behind. Seven consonant sounds ended up written twice over, once with a high-class letter and once with a low-class letter: kh, ch, s, th, ph, f and h. These are sound groups rather than neat pairs, and they are uneven. The sound th is written ถ and ฐ on the high side against ท ธ ฑ ฒ on the low. The sound s is ส ศ ษ high against ซ alone. Do not expect one letter to face exactly one other; expect a high side and a low side. The two sides sound identical, but they answer to the same tone mark differently, and they differ again when no mark is written. Between them the group spells tones neither side could reach alone. Take the sound khaa. คา, low class with no mark, is mid (khaa, to be stuck). ขา, high class with no mark, is rising (khǎa, leg). ข่า, high class with mái èek, is low (khàa, galangal). ค่า, low class with that same mái èek, is falling (khâa, value). ค้า, low class with mái thoo, is high (kháa, to trade). One sound, five tones, five real words. Alone, ข reaches rising, low and falling. Alone, ค reaches mid, falling and high. Each covers the other's gaps. The middle class behaves more plainly, and it is these nine letters: ก จ ฎ ฏ ด ต บ ป อ. In Thai schools they are held as one sentence, ไก่จิกเด็กตายเด็กตายบนปากโอ่ง, where each word begins with one of them and the repeated เด็กตาย covers ด ฎ and ต ฏ. A middle-class letter takes all four tone marks, and on it the marks and the tones line up by number. The marks are named one, two, three and four: mái èek, mái thoo, mái dtrii, mái jàt-dtà-waa. The tones carry the same numbers: siang èek is low, siang thoo is falling, siang dtrii is high, siang jàt-dtà-waa is rising. So on a middle-class letter, mark one gives tone one, mark two gives tone two, and so on down. Unmarked in a live syllable it is mid, siang sǎa-man. A middle-class letter therefore reaches all five tones on its own, with nothing hidden, which is why it is the class to start with. Class never decides a tone by itself. It works with three other things: whether the syllable is live or dead, the length of the vowel, and which tone mark, if any, is written. A dead syllable ends in a p, t or k stop, or in a short vowel with nothing after it. A live syllable ends in a long vowel, or in m, n, ng, y or w. One exception arrives immediately: ไ-, ใ-, -ำ and เ-า are short but live, because they end in y, w or m. Without that exception you would make ใจ dead and say jài; the word is jai, mid. Likewise ไป is bpai and เขา is khǎo. Vowel length matters mainly in dead syllables with a low-class initial, where a short vowel gives high and a long vowel gives falling. The full grid is on the Thai tone rules page. Ten low-class letters have no high-class counterpart: ง ญ ณ น ม ย ร ล ว ฬ. Thai calls them อักษรเดี่ยว, the single letters, as against the fourteen อักษรคู่ that do have a high-class letter for the same sound. They are the voiced continuants: the nasals, the liquids and the glides. The writing system covers the gap with a silent ห written in front, which makes the syllable follow the high-class row. It is not pronounced. In practice you meet it before eight of the ten, in the combinations หง หญ หน หม หย หร หล หว; ณ and ฬ occur almost entirely in words borrowed from Pali and Sanskrit and do not take it. หมา is mǎa, dog, with a rising tone that ม could never produce alone: มา, the same letter and vowel without the ห, is maa, mid, and means to come. หนู is nǔu, rising. But the leading ห predicts the high-class row, not the rising tone: a mark still applies, so หน่อย is nàwy, low, because a high-class initial with mái èek gives low. Two mistakes follow from reading the ห as a letter rather than as a signal: pronouncing it, or ignoring it and reading the word on the low-class row. A silent อ does the same job in exactly four words: อยาก (yàak, to want), อยู่ (yùu, to be somewhere), อย่า (yàa, do not) and อย่าง (yàang, sort, kind, way). อ is middle class, so these syllables follow the middle row, and all four come out low. Check them against a word you probably know: ยาก, the same ย without the leader, is yâak, falling, and means difficult. There is no fifth word, so learn the four as a closed list and stop looking for a rule. Class belongs to the initial consonant of a syllable, and only to the initial. A consonant in final position does not bring its class with it; there it does a different job, deciding whether the syllable is live or dead. In นก (nók, bird) the class that counts is the low class of น; the final ก only makes the syllable dead, and a low-class initial with a short vowel in a dead syllable gives high. Two consonants at the start need care, because three different things look alike. In a true cluster, pronounced together, the first carries the class for the whole syllable: ปลา is bplaa, กรอบ is gràwp. Where the two split into two syllables across an unwritten vowel, the first governs the second only when the second is one of the ten unpaired low letters: ขนม is khà-nǒm, the rising tone coming from ข and not from น; ตลาด is dtà-làat; ผลิต is phà-lìt. When the second consonant belongs to any other class it keeps its own: สบาย is sà-baai, not sà-bǎai, because บ is middle class and stays middle class. Two spellings to know as exceptions: ทร is read as s (ทราย, saai, sand), and the ร is silent in สร- (สร้าง, sâang, to build). The tone-rules page covers the leading-consonant pattern in full. Learn the classes the way they are taught in Thailand: two fixed sentences and a residue. The nine middle-class letters are the sentence above. The eleven high-class letters are ผีฝากถุงข้าวสารให้ฉัน, seven words giving ผ ฝ ถ ข ส ห ฉ, with ฃ ฐ ศ ษ attaching to the letter they share a sound with. Everything outside those two sentences is low class. That is the whole system, and it means the low class, the largest at twenty-four, never has to be memorised as a list. Start with the middle nine, because that is the class where every mark behaves transparently and every syllable is fully derivable. Take the high sentence next. Then take the eight ห combinations as a third block, since they are how the high-class row reaches the sonorants. At first you will derive every tone consciously: find the initial, name its class, check the ending, check the mark. What changes with reading volume is not the knowledge but the speed of that derivation, until you see a leading ห and expect the high-class row before you have finished the word. Expect weeks rather than days, and note that reading a tone correctly and saying it correctly are separate skills. This page gives you only the first. The letters themselves, with their names and classes, are on the Thai alphabet chart. If you are starting from nothing, Read Thai introduces the script in an order that makes the classes usable rather than abstract, and Thai tone rules is the page that turns all of this into a tone.