The Letter Yod (Yud) (י)
This is the tenth letter of the Hebrew alphabet (Aleph-Bet), so its numerical value is 10. (Please note that most Israelis pronounce the name Yud).
According to the Jewish sages, the yod represents the world to come and completeness. The yod is the most frequently used letter in the Aleph-Bet, as it appears in Hebrew texts approximately 11% of all the letters. This letter is unique in its appearance. It is the smallest letter of the Aleph-Bet, and is therefore considered to be “modest.” It also symbolizes wisdom, and it illustrates this by being small, like the small quantity of truly wise individuals.
According to the Talmud (the central text of Rabbinic Judaism), the letter yod wanted to be the first letter of the Aleph-Bet. It asked this of the Creator of the world but was turned down. The Creator then comforted the letter yod, with the fact that it is the first letter of His name, and even appears twice in the divine name. Since the yod is so small, it also represents the super-natural, the things that are above the physical dimension.
The letter yod is used in the Hebrew expression: קוֹצוֹ שֶׁל יוֹד (kotzo shel yod). Literally translated as the smallest edge of the letter yod. This expression is used to refer to something tiny, insignificant, or inconsequential.
It is interesting to note, that in most sacred literature, the pages are marked with letters, instead of numbers. (There are some books that use both formats.) When they get to the number 15, which would be the letters “י-ה,” the printers avoid using this letter combination, since it is also one of the names of the Almighty. It is customary to instead use the letters ט”ו (numerical value 9+6 also equal to 15). Similarly, in the Jewish calendar, the 15th day of a month will be called ט”ו and not י-ה.