Gre-gō'ri-an, a.

a. [N. Lat. Gregorianus, from Gregorius, Gr. Γρηγόριος, Gregory, from γρηγορεῖν, to be awake, ἐγρήγορα, perfect of ἐγείρειν, to awaken; It. & Sp. Gregoriano, Fr. Grégorien.] Belonging to, or established by, Gregory.

Gregorian calendar, the calendar as reformed by Pope Gregory XIII. in 1582, including the method of adjusting the leap-years so as to harmonize the civil year with the solar, and also the regulation of the time of Easter and the movable feasts by means of epochs.—Gregorian chant (Mus.), choral music, according to the eight celebrated church modes, as arranged by Pope Gregory I. — Gregorian telescope (Opt.), a form of the reflecting telescope, so named from its inventor, Prof. James Gregory, of Edinburgh. A small concave mirror in the axis of this telescope, having its focus coincident with that of the large reflectors, transmits the light received from the latter back through a hole in its center to the eye-piece placed behind it. — Gregorian year, the year as now reckoned according to the Gregorian calendar. Thus, every year which is divisible by 4, except those divisible by 100 and not by 400, has 366 days; all other years have 365 days.