"A pyramid (from Greek: πυραμίς pyramis)[1][2] is a structure whose outer surfaces are triangular and converge to a single point at the top, making the shape roughly a pyramid in the geometric sense. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape"
"In geometry, a pyramid is a polyhedron formed by connecting a polygonal base and a point, called the apex.
[...]
When unspecified, a pyramid is _usually_ assumed to be a regular square pyramid"
"A pyramid (from Greek: πυραμίς pyramis)[1][2] is a structure whose outer surfaces are triangular and converge to a single point at the top, making the shape roughly a pyramid in the geometric sense. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape"
https://en.wikipedia.org/wiki/Pyramid_(geometry):
"In geometry, a pyramid is a polyhedron formed by connecting a polygonal base and a point, called the apex. [...] When unspecified, a pyramid is _usually_ assumed to be a regular square pyramid"
Note the _usually_.