Glossary
Z
A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, Y, Z

Zenith—THe highest point directly above your head, opposite the nadir. This is opposed to the midheaven (Medium Coeli, which is the high point of the Sun's path).
Zodiac—Greek for 'circle of animals'. The belt of constellations in the sky roughly above the equator.
Zodiac, Sidereal—This system is most commonly used in Eastern astrology. Each spring the constellations have moved. In the sidereal zodiac, the boundaries of each star sign move with the constellations. So the start date of each star sign slowly changes. See also Precession.
Zodiac, Tropical—The system is most commonly used in Western astrology. The star sign boundaries are dictated by the same date and fixed to the start of spring. See also Precession.