X-Z:

Yang: said of the male polarity of the yang-yin duality of male-female, active-passive, father-mother, hot-cold symbolized in the Taoist symbol of the interlocking curved water drops within a circle. In astrology, the Sun as the source of outpouring energy and heat symbolizes yang; astronomically it is the yang center of the solar system.

Yin: said of the female polarity of the yang-yin duality of male-female, active-passive, father-mother, hot-cold symbolized in the Taoist symbol of the interlocking curved water drops within a circle. The Earth, comprised of the substance acted upon and animated by the Sun's energy, is the yin center of the solar system. Astrologically, the Moon serves as the primary symbol of yin in a horoscope chart.

Yod: see "Finger of God": A triangular aspect structure: one planet at the vertex in quincunx to two others in sextile. The whole structure points to the planet at the apex: a special task in life beneficial to one’s evolution; thought to be a fateful, constant, and relatively unchanging condition. There are many vague and conflicting opinions as to the symbolism of the Yod among modern astrologers, suggesting that it is not well understood.

Zenith: the point on the celestial sphere that - determined by gravity - is directly overhead. The zenith is specific to each given locality, and changes, just as does the local horizon, as we move about on the surface of the Earth. The zenith is also marked by the intersection of the prime vertical with any local meridian plane. 

Zodiac: (from the Latin, "band of animals"); those particular constellations, only 12 in number, through which the Sun, Moon and all the planets appear (as seen from the Earth) to move year after year. The planets move only through these 12 constellations due to their orbits all being contained in an infinitely large flat surface called the plane of the ecliptic. This in turn is thought to result from the planets all having condensed from the gaseous equatorial plane of a protostar billions of years ago, the center of which is now the Sun. Being composed of "fixed" stars and their geometrical relationships to each other, the zodiacal signs remain unchanged over thousands of years. The astrological signs, however, shift one sign relative to the constellations approximately every 2100 years due to the precession of the equinoxes.