Annual Constituent (of tide). That part of a tidal undulation that varies with Earth's distance from Sun.
Annual Inequality. Variation in a tidal undulation that is more or less seasonal and periodic.
Annual Parallax. Apparent displacement of a heavenly body from its true position when caused by Earth's elliptical movement around Sun. Is negligible in stars.
Annular Eclipse. Moon's occultation of Sun when outside edge of Sun's disc is unocculted although centres of both bodies are in line. Due to Moon's diameter being less than diameter of Sun, through Moon being in or near apogee.
Anomalistic.Irregular: uneven. Applied to motions, intervals and values that are basically uniform but are made irregular through the action of one or more disturbing factors.