Chai, the Number of Life

Eighteen is, in Jewish tradition, the number of life. The Hebrew word chai, meaning alive or living, is spelled chet and yod, whose gematria values of eight and ten total eighteen; the word is worn as an amulet and the number treated as auspicious, which is why charitable gifts and wedding cheques are so often given in multiples of eighteen, chai, double chai, and so on. This is one of the clearest cases in which a number acquires meaning purely through the numerical value of a word, the technique of gematria, rather than through counting anything. The association is genuinely traditional and still in everyday use, and it makes eighteen almost the opposite of an unlucky number in Jewish life: a small sum given as a blessing.

Chai's gematria of eighteen is the clearest possible illustration of Kabbalistic method for a general reader, and it has a documented modern civic afterlife: American Jewish charitable and political giving is conventionally reckoned in multiples of eighteen, a eighteen-dollar or one-hundred-and-eighty-dollar donation read as symbolically doubling or tenfold-ing life itself, a twentieth-century American custom built directly on an ancient technique rather than a survival from it.