Gematria or gimatria is a system of assigning numerical value
A number is a mathematical object used to count and measure. In mathematics, the definition of number has been extended over the years to include such numbers as zero, negative numbers, rational numbers, irrational numbers, and complex numbers....

 to a word or phrase, in the belief that words or phrases with identical numerical values bear some relation to each other, or bear some relation to the number itself as it may apply to a person's age, the calendar year, or the like. It is likely that the term derives from the order of the Greek alphabet, gamma being the third letter of the Greek alphabet (gamma + tria).