WAW (ו):
Sixth letter of the Hebrew alphabet. The name possibly means "nail" or "hook," and the shape of the letter in the Phenician alphabet bears some resemblance to a hook. "Waw" is a labial spirant, identical in sound with the English "w." When preceded by the labial vowel "u," it blends with it ("uw"), the result being a long u-sound; and when an a-vowel precedes it, the two form the diphthong "au," which in Hebrew has passed into "o." At the beginning of a word (a position it rarely has in Hebrew) "waw" retains its consonantal value, except when followed by פ, נ, מ, or a letter with simple "shewa." As the first letter of verb-stems it has been replaced in Hebrew almost everywhere by "yod." As a numeral (in the later period) "waw" has the value of 6.
