Acanthus: an herbaceous plant with large, glossy leaves with an oblong shape and quite jagged edges.  Due to its remarkable decorative effect, it found widespread use as an ornamental pattern in architecture and painting, from the Hellenistic period onwards.

Apse: an architectural structure generally formed like a semicircular wall covered by a half dome vault. In Christian churches it is usually found at the back of the nave to delimit the space behind the altar.