See caption
Open pediment above a first-floor window of the Masonic Temple in Aberdeen, Scotland
Wikimedia Commons

A pediment is a low-pitched gable above a portico
Porch leading to the entrance of a building, its roof supported by columns and with a pedimented gable.
or façade. Most pediments take the form of a flattened isosceles triangle.[1] An open pediment is one in which the base of the triangle is missing; a broken pediment is one with its apex missing, replaced by a circular segment.[2]

Pediments are found in ancient Greek architecture from as early as 580 BCE, as in the archaic Temple of Artemis, Corfu, which was probably one of the earliest.[3]