ZAYIN 

Pronunciation: Za-yin
Numerical value: 7
Primary meaning: weapon
Secondary meanings: Crown, species
Essence: Motion
Astrological continuum: Gemini, the twins
Time continuum: Sivan (the month in which God said the Ten Commandments)
Soul continuum: the left foot
Sephirot: Path between Wisdom (Chochmah) and Power (Gevurah)
Verse from the Torah: God called the light day.
Form: A letter Vav whose head wears a crown and sees in all directions.
Sefer Yetzira (Book of Creation)

Sivan is the month of the twins, Gemini. The epitome of the twins in the Torah is Jacob and Esau who are in a constant struggle for supremacy. Jacob represents the Godly inclination and Esau is the animal inclination. Zayin is the weapon with which one fights this battle because Zayin is 7, corresponding to the totality of the emotional attributes which one must constantly refine.  

The letter Zayin symbolizes agility and travel. Zayin is a male letter, and represents a masculine ego. One whose name starts with Zayin enjoys motion and interaction; they have a way with words and express themselves distinctively. They have a thirst for all types of knowledge, but do not delve too deeply. Easily disinterested, they immediately search for something new. (Shemot Bnei Adam)