Devanagari U उ

Short u is the fifth letter of the varnamala and the third of the three simple vowels named at the head of Panini's Shivasutras, after a and i. The Sanskrit phoneticians class it as labial, oshthya, because it is formed with the lips rounded, and their scheme sets it in the same articulatory family as the labial consonants pa, pha, ba, bha and ma. Its vowel sign departs from the pattern of the vowels before it: instead of standing beside the consonant it hangs beneath it, a small hook attached to the foot of the letter.

Devanagari uses the space above and below the line for vowel signs as freely as the space beside it, which is one of the features that gives a page of the script its layered look and one of the reasons the headline running along the top of a word is so useful as an anchor. The independent letter shown here is written only where the vowel opens a word or follows another vowel. In the pattern of the varnamala, u completes the set of three basic vowel qualities, throat, palate and lips, from which the grammarians derive the rest: the diphthongs are analysed as combinations of a with i and with u, so that the whole vowel system is built from these three positions and the distinction of length.

When Om is written out as three sounds rather than as a single ligature, u stands in the middle, between a and m. The Mandukya Upanishad is the text that develops that analysis furthest, taking the syllable apart and correlating each of its three parts with a state of consciousness: a with waking, u with dream, m with deep sleep, and the silence that follows with a fourth state it does not name except as the fourth.

Later commentary built extensively on that scheme, and it is the source of most of the further correspondences attached to the syllable in the Vedantic literature. The correlation belongs to that text and its tradition of commentary, and this atlas records it as theirs. Sanskrit grammar contributes a second reason the sound sits where it does in the syllable. Under the rules by which vowels combine, a followed by u yields the diphthong o, so the written form of Om is the outcome of the same rule that operates everywhere else in the language, and its three-part analysis is a reading back of the syllable into the sounds that would have produced it.

In the Tantric arrangement of the letters, u belongs with the other vowels to the class held to precede the consonants, and it is one of the fifty matrika counted in the garland. Individual schools attach further attributions to it; those attributions are the schools', and are described in the scholarly literature rather than harmonised by it.