Chai is a symbol and word that figures prominently in Jewish culture and consists of the letters of the Hebrew alphabet Het and Yod (?). In the Hebrew language, the word chai spelled by these two letters meaning "living," which is related to the term for "life." There have been various mystical numerological speculations about the fact that, according to the system of gematria, the letters of chai add up to 18. For this reason, 18 is a spiritual number in Judaism, and many Jews give gifts of money in multiples of 18 as a result. The Chai symbol is often worn by Jews as a medallion around the neck, along with the Star of David (Magen David) and the Hamsa.