numerologia
Gematria
Gematria is the Jewish practice of assigning a numerical value to each letter of the Hebrew alphabet (aleph 1, beth 2, ..., yod 10, ..., tav 400) and reading sacred words through the numbers they generate. It is part of the exegetical tradition of Kabbalah and of other forms of rabbinic exegesis.
Systems of calculation
Classical gematria sums the values of the letters of a word. There are more complex variants (mispar gadol, mispar katan, mispar siduri) with different rules. When two words have the same numerical value, one speaks of gematric equivalence: they are taken to share something in meaning as well.
Tradition and use
Gematria is used in Talmudic commentaries and in Kabbalah to discover hidden meanings in Scripture. In Christianity it is remembered for the "number of the beast" (666) in the Apocalypse of John. In contemporary culture it is the object of popular interest, although its mystical "revealing" uses have no scientific basis.
FAQ
Does it work in other languages?
Gematria is specific to Hebrew. Analogous practices exist in Greek (isopsephy) and Arabic (abjad), but they are not "the same thing".
What is 666?
In the Christian Apocalypse it is the "number of the beast". Gematric exegesis has proposed various historical candidates (Nero in Hebrew yields 666 with a particular transliteration).
Is it pseudoscience?
As a mystical reading technique of Scripture it belongs to religious tradition, not to science. As a universal "predictive" tool it cannot be validated.