obsequies (Lat. obsequia, "services, observances")

    Rites performed for the dead.

ogee arches

    arches composed of two double-curved lines that meet at the apex.

oil paint

    a painting medium in which pigments are mixed with drying oils, such as linseed, walnut, or poppy. Though oils had been used in the Middle Ages, it was not until the van Eyck brothers in the early 15th century that the medium became fully developed. It reached Italy during the 1460s and by the end of the century had largely replaced tempera. It was preferred for its brilliance of detail, its richness of colour, and its greater tonal range.

Oratorians (or the Congregation of the Oratory)

    In the Catholic Church, an order of secular priests who live in independent communities, prayer and preaching being central to their mission. The Oratorians was founded by St Philip Neri (1515-1595).

oratory (or oratorium)

    A place where Oratorians pray or preach; a small private chapel.

orders of architecture

    In classical architecture, the three basic styles of design. They are seen in the form of the columns, capital, and entablatures. The earliest, the Doric order, was the simplest, with a sturdy, fluted column and a plain capital. The Ionic order had a slenderer column, a more elaborate base, and a capital formed by a pair of spiral scrolls. The Corinthian order was the most ornate, having a very slender column and a capital formed of ornately carved leaves (acanthus).

original sin

    The tendency to evil transmitted to mankind by Adam and Eve's transgression in eating of the Tree of Knowledge; inborn sin.

Our Lady of Sorrows (or Mater Dolorosa)

    A depiction of the Virgin Mary lamenting Christ's torment and crucifixion. There are several forms: she can be shown witnessing his ascent of Calvary; standing at the foot of the Cross; watching as the body of Christ is brought down from the Cross (Deposition); or sitting with His body across her lap (Pietà).