What does the term 'architrave' specifically denote?

The term 'architrave' specifically denotes the lower part of an entablature, which is a crucial element in classical architecture. The architrave serves as the beam that rests directly on the columns and supports the structure above it, typically the frieze or cornice. In classical design, the architrave is often plain or can feature decorative elements, but its primary function is structural, providing a transition between the vertical columns and the horizontal entablature that follows. This element is commonly found in temples and other classical buildings, acting as a foundational component to the overall architectural integrity and aesthetic appeal.

The other choices do not relate to the definition of architrave in traditional architectural terminology. The capstone of a fortified hill refers to a different context entirely, commonly associated with defensive structures rather than classical design elements. A type of masonry joint pertains to construction techniques and methods, while a decorative roofing element does not accurately represent the specific role of the architrave within an architectural framework.