"Marker" - Any non-tomb mortuary structure which marks a below-grade burial, but does not contain an interment and whose form is often sculptural.

Simple Marker: A single element marker

Headstone/footstone: An associated pair of upright slabs, usually of different height embedded in the ground or in a separate stone base, which defines the grave and is inscribed.

Stele: A carved or inscribed stone slab or pillar used for commemorative purposes, taller and thinner than a headstone. Base not required.

Plaque: Non-freestanding plain or ornamental tablet affixed to a wall or structure, but not a tomb/marker.

Other: Any single architectural or sculptural form.