ד (or Dalet, Daled) The fourth letter of the Hebrew alphabet, ד Daleth symbolizes "a door." When adapted to Greek, it became the letter Delta (a triangle).
Daleth is related with:
In Kabbalah, the letter Daleth represents a youth, the terrestrial man, who receives charity from his heavenly man, his letter Gimel. For this, Shaddai El Chai must stand at the open door (Daleth) of the entrance of his house (physical body).
The Kabbalistic value of Daleth is 4.