A pyramid
A (Square) Pyramid
Pyramid
sphere
A Square Pyramid.
That's a pyramid.
There is a contradiction in your question. If the base has four equal sides then is it a square so not all the faces are Triangles. However if the base is a square and the rest of the faces are triangles then your object is a "Square-based Pyramid"
square base pyramid and a triangular base pyramid
The figure is a pyramid and the base is a square.
A pyramid. The square being the base and the triangles the 'sides' - each having a side connected to a side of the square - the other sides connected to 'neighbor-triangles'.
Pyramid. Work: 4 sides (that you usually see) are triangles, the base (bottom) is a square
Not necessarily. The solid could be a square based cuboid (hexahedron).