The Tibetan alphabet was created in the mid-7th century, by Thonmi Sambhota, a Tibetan official, with the assistance of some Indian Buddhist monks. The letters, which are a form of the Sanskrit characters of that period, rammar, follow the same arrangement as their Sanskritic prototype. The printed form of the script used in religious texts is called u-can or u-chen while the hand-written cursive form used in everyday writing is called u-mey.

A note on the transliteration of Tibetan. When attempting to transliterate Tibetan using a Latin script one is faced with an immediate problem: should the transliteration reflect how a word is pronounced or how it is spelled? Like English, Tibetan suffers from a wide divergence between the two so a choice must be made. Tibetan scholars have settled on the Wylie transliteration scheme which is useful for reconstructing the original Tibetan sequence of letters, but near useless in indicating pronunciation (unless you take it upon yourself to study the irregularities of Tibetan spelling). This accounts for the stunningly unpronounceable transliterations often encountered in the course of Tibetan studies. The remainder of this article uses the Wylie system, which nonetheless serves adequately when describing Tibetan letters in isolation.

The 30 consonants, which are deemed to possess an inherent sound a, are the following:

ka, k’a, ga, nga (n¯a),
ha (ca), ha (cha), ja, nya (ña),
ta, t’a, da, na,
pa, p’a, ba, ma,
tsa, ts’a, dza,
wa, z’a (ža), Ia (za),
‘ha ('a), ya, ra, Ia,
s’a, Ia (sa),
ha, a.

The apostrophe (’) can also be Romanized as h, and signifies aspiration.

In addition to the simple consonants above there are 90 conjunct consonants which represent clusters of consonants (e.g. "swa", "ska", "sga", "sna", "spa", etc.). Each of these combinations is represented by its own unique glyph in the alphabet. The large number of conjunct consonants is what makes the Tibetan alphabet more difficult to learn than many other alphabets. As with simple consonants, if no vowel mark is added the conjuct consonant is assumed to be followed by a short 'a'.

Consonantal letter variations include:

The "Sanskrit cerebrals" are represented by the letters, ta La, do, na, s’a, turned the other way.

Va, when combined as second consonant with k-, p-, m-, is written under the first letter.

Ra, when combined as second letter with k-, t-, p-, is written under the first, and when combined with another consonant as first letter over the second.

The vowels are a, i, u, e, o, which are not distinguished as long or short in writing, except in loanwords, especially transcribed from the Sanskrit. Though they are so in the vernaculars in the case of words altered by phonetic detrition.

Syllables are separated by a dot, and tones are unmarked in writing.

~from Wikipedia

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