what is a tetrahedron ?

Answer 1

A tetrahedron is a solid with four faces. Tetra- means four, -hedron means solid geometric object.

You can also think of it as a triangular pyramid.

Answer 2

According to the Miriam-Webster's Collegiate Dictionary a Tetrahedron is a solid contained by four plane faces; a triangular pyramid. Also, any of various objects resembling a tetrahedon. A real world example: The Great Pyramid at Giza in Egypt.

Answer 3

tetra = 4
hedron = face

A four-faced figure, particularly, if its regular the faces are equilateral triangles. Put four index cards in a pile and try to cut an equilateral triangle (a triangle with all sides the same length and 60 degree angles.) Then take one of the triangles and place it on the table. Next, take the other three triangles and stand each one up at each one of the sides of the triangle on the table and let them lean inward. Use a little tape or glue and you have a tetrahedron.

Answer 4

A tetrahedron (plural: tetrahedra) is a polyhedron composed of four triangular faces, three of which meet at each vertex. A regular tetrahedron is one in which the four triangles are regular, or "equilateral," and is one of the Platonic solids.

Answer 5

A space figure composed of 4 points and 4 faces.

Answer 6

Four (triangular) faces, four vertices (corners), six edges.

For extra credit, look up the Euler-Descartes formula for polyhedra.
http://en.wikipedia.org/wiki/Euler_characteristic

Answer 7

a 20 sided cube