### Nondimensionalization

(manipulation of an equation to remove dimensions)

**Nondimensionalization** is the transformation of an equation to an
equivalent equation, eliminating some or all the variables that
have units (e.g., seconds, meters, kilograms, etc.). This may be
to simplify the equation and/or to make apparent the modeled
phenomenon's intrinsic characteristics. In place of the variables
with units may be variables with ratios.

Such a ratio may be between values in the original equation that
have similar units, but the equation may need to be recast first
so as to provide two such values. If such a means is not evident,
a quantity may be chosen to form such a ratio, e.g., one that has a
natural significance, but other times, a seemingly-arbitrary quantity
is chosen and the "nondimensionalization" seems little more than
merely adopting new units. For example, expressing a speed as a
ratio with c might make the physics more evident, while expressing
it as a ratio with "1000 meters per second" seems to be little more
than changing to a more convenient unit.

(*mathematics,technique*)
http://en.wikipedia.org/wiki/Nondimensionalization

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