Decimation (
decimatio;
decem = "ten") was a form of military discipline used by senior commanders in the Roman Army to punish units or large groups guilty of capital offences, such as mutiny or desertion. The word
decimation is derived from Latin meaning "removal of a tenth".
The procedure was a pragmatic, yet vicious, attempt to balance the need
to punish serious offences with the practicalities of dealing with a
large group of offenders.
A cohort (roughly 480 soldiers) selected for punishment by decimation was divided into groups of ten; each group drew lots (sortition), and the soldier on whom the lot fell was executed by his nine comrades, often by stoning or clubbing. The remaining soldiers were often given rations of barley instead of wheat
(the latter being the standard soldier's diet) for a few days, and
required to camp outside the fortified security of the marching camp.
Because the punishment fell by lot, all soldiers in a group sentenced
to decimation were potentially liable for execution, regardless of
individual degrees of fault, rank or distinction.
If ever these same things happen to occur among a large group of men...
the officers reject the idea of bludgeoning or slaughtering all the men
involved [as is the case with a small group or an individual]. Instead
they find a solution for the situation which chooses by a lottery system
sometimes five, sometimes eight, sometimes twenty of these men, always
calculating the number in this group with reference to the whole unit of
offenders so that this group forms one-tenth of all those guilty of
cowardice. And these men who are chosen by lot are bludgeoned
mercilessly in the manner described above.
In digital signal processing,
decimation is the process of reducing the sampling rate of a signal.
Complementary to interpolation, which increases sampling rate, it is a specific case of sample rate conversion in a multi-rate digital signal processing system. Decimation utilises filtering to mitigate aliasing distortion, which can occur when simply
downsampling a signal.
A system component that performs decimation is called a
decimator.