U: The Labial Vowel and the Sign Beneath the Letter

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.