**Occam's Razor**
The principle that when faced with multiple but equivalent
interpretations of some phenomenon, one should always choose the
simplest explanation that correctly fits the data. Occam's Razor is
useful for selecting competing models for some phenomena.

**One-to-One**
A function or map that for every possible output has only
one input that yields that particular output; if *f(a) = f(b)*, then
*a = b*.

**Optimization**
The process of finding parameters that minimizes or maximizes a
function.

**Outer Product**
An operation on two vectors that yields a matrix. Given two
vectors with the same dimensionality, the outer product is a square
symmetric matrix that contains the product of all pairs of elements
from the two vectors, i.e., *A[i,j] = x[i] y[j]*.