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I was just reading about polyhedrons and wondered, even though it's an impossible shape, what a 3-hedron is called? I'm really asking what the Greek for '3'. Does it just converge to a triangle?

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"tri" seems like the right prefix, coming from Latin and Greek. –  Dylan Moreland Jan 8 '12 at 4:52
    
That was my first thought, though thought 'tri' was only Latin. –  Korgan Rivera Jan 8 '12 at 4:54
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A relevant reference: en.wikipedia.org/wiki/Number_prefix –  Jonas Meyer Jan 8 '12 at 4:57
    
how about three-hedron? lol –  Mehrdad Jan 8 '12 at 4:57
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@J.D.: No, tetrahedrons have 4 faces, not 3. The question is at face value asking about an object that doesn't exist, but is really asking about a prefix meaning $3$. –  Jonas Meyer Jan 8 '12 at 5:14
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up vote 4 down vote accepted

Tri- is the greek prefix.

We do use the word trihedron, but to refer to something slightly different: the Frenet-Serret trihedron.

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