by various authors, A Dictionary of Greek and Roman Antiquities… (1890)
“ A potter's wheel is described, in the Anthology, as κύκλος ἁψῖδος. The next transition of meaning is to anything vaulted (for example, ἡ ὑπουρανία ἁψίς, the vault of heaven, Plat. Phaedr. p. 247 b) ; and in this sense it was adopted in architecture, first, for any building or portion of a building of a circular form, or vaulted (Plin. Ep. 2.17.18) , and more especially for the circular and vaulted end of a Basilica. (Paul. Nol. Ep. 12; Augustin, Ep. 203; Isid. Orig. 15.8.) For the application of the word in Christian churches, see Dict. of Christ. Ant. ”
