Mold
A mold is the pre-cut metal shape into which plastic is injected to manufacture the parts for a given Transformers toy. Since the very beginning of the Transformers brand, many pairs (or even groups) of toys have been variations on a single mold. (Indeed, many pre-Transformer Diaclone and Microchange toys were also available in multiple officially sanctioned color schemes.)
Redecos
In most relevant cases, a mold will be used as the basis for two or more individual toys distinguished mainly by their color schemes, and sometimes also by a permanently attached accessory such as an emergency-vehicle light bar. Such toys are called redecos.
Retools
In the case of retools, the basic shape of the original mold is used, but with physical changes to certain parts. In extreme but rare cases, a mold will be retooled so thoroughly as to change the toy's transformation mechanics, as happened with Pipes and Dark Crumplezone.
See also
