The fifteenth path joins Chokmah, Wisdom, to Tiphareth, Beauty, descending the right side of the Tree from the supernal father to the harmonising centre. It carries the letter Heh, whose name means "window", the opening through which light and breath pass, and which in Hebrew grammar marks the definite article and, doubled in the divine name, the feminine and the breath of life.
In the Sefer Yetzirah Heh is one of the twelve simple or single letters, and these twelve are assigned to the twelve signs of the zodiac; Heh is given to Aries, the first sign, the ram, the beginning of the zodiacal year. The letter-to-sign attribution is part of the ancient Jewish scheme in which the alphabet builds the cosmos: three mother letters for the elements, seven doubles for the planets, and twelve simples for the signs of the zodiac, each letter a creative channel and each simple letter a month, a sign and a faculty of the body.