In geometry, an apex (plural apices) is the vertex which is in some sense the "highest" of the figure to which it belongs. The term is typically used to refer to the vertex opposite from some "base". The word is derived from the Latin for 'summit, peak, tip, top, extreme end'.

The apex and base of a square pyramid

Isosceles triangles

In an isosceles triangle, the apex is the vertex where the two sides of equal length meet, opposite the unequal third side.[1]

Pyramids and cones

In a pyramid or cone, the apex is the vertex at the "top" (opposite the base).[1] In a pyramid, the vertex is the point that is part of all the lateral faces, or where all the lateral edges meet.[2]

References

Weisstein, Eric W. "Apex". Mathworld.

Jacobs, Harold R. (2003). Geometry: Seeing, Doing, Understanding (Third ed.). New York City: W. H. Freeman and Company. pp. 647, 655. ISBN 978-0-7167-4361-3.

Undergraduate Texts in Mathematics

Graduate Studies in Mathematics

Hellenica World - Scientific Library

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