After classifying 3-dimensional hyperbolic Coxeter pyramids by means of<br />
elementary plane geometry, we calculate growth functions of corresponding<br />
Coxeter groups by using Steinberg formula and conclude that growth rates of<br />
them are always Perron numbers. We also calculate hyperbolic volumes of them<br />
and compare volumes with their growth rates. Finally we consider a geometric<br />
ordering of Coxeter pyramids comparable with their growth rates.