#celestial mechanics

• Anomaly — A deviation from a norm, from a rule, or from natural laws of development; irregularity, strangeness, structural or functional non-conformity. In medicine, the term denotes a congenital malformation, anatomical asymmetry, or biological disruption present from birth. In astronomy, it represents a structural angle used to determine the exact position of a celestial body on its elliptical orbit relative to the periastron.
• Anticenter — A geometric or astronomical point situated in direct opposition or diametrically opposite to a predetermined center of gravity, geometric center, or focal point. In astronomy, the term often describes the galactic anticenter, meaning the direction on the celestial sphere located exactly 180 degrees away from the geometric center of the Milky Way, positioned toward the Auriga constellation.
• Antiscian — A classical geographical and astronomical term denoting inhabitants or points on the Earth's surface located on the same meridian but in opposite hemispheres (Northern and Southern), at equal distances from the equator (sharing the same numerical latitude). Structurally, antiscian points experience noon at the exact same moment, but their seasons and night lengths are completely reversed; in ancient astrology, it defined zodiacal points reflected symmetrically across the solstitial axis.
• Apocenter — The point in the elliptical orbit of a celestial body or an artificial satellite that is farthest from the center of attraction; the extremity of the orbit's major axis opposite to the pericenter. Depending on the central body around which the orbital motion takes place, the term takes specific names, such as apogee for Earth or aphelion for the Sun.
• Apogalacticon — The point in the elliptical orbit of a star, a stellar cluster, or a celestial body orbiting a galaxy's nucleus that is farthest from the galactic center; galactic apoapsis. In stellar dynamics, this point represents the moment when the body's orbital velocity reaches its minimum value due to the maximum distance from the central mass.