decimate is a word with two meanings, one in use in everyday English, the other â€˜correctâ€™, according to pedants and other academics. (It is an interesting test case of what it means to say that a word is â€˜correctâ€™, and a good example of how this varies according to context.)
- The original meaning was â€˜to punish [a military unit] by killing every tenth man.â€™ This was a salutary lesson taught to a unit in the army of imperial Rome, about 2,000 years ago. If the unit showed cowardice, for example by running away in a battle, and was judged to have behaved disgracefully, it was paraded in lines. Officers then marched between the lines and killed every tenth man they passed. That at least is the story I was taught as a boy, however unlikely it seems to me now that soldiers were well enough trained to stand still for this punishment to be inflicted. However, my Latin teacher may well have meant to impress on me the marvellous discipline of the Romans.
The meaning developed in certain figurative directions. In more modern times an army could be â€˜decimatedâ€™ by the enemy â€“ i.e. lose about 10% of its men; or a business could have its profits decimated by tax â€“ i.e. the government would take a tenth of them.
This meaning â€“ â€˜to take a tenth ofâ€™ â€“ with its link to the original is of course the meaning preferred by academics.
- However, the general public in its use of English wants the word â€˜decimateâ€™ to sound terrible, and such is the modern world that a tax rate of 10% no longer sounds terrible. It actually sounds quite attractive! Alas, military losses of 10% no longer sound awful either. So the modern use of â€˜decimateâ€™ is â€˜to suffer very heavy lossesâ€™.
The on-line version of Fowler suggests that this secondary meaning has replaced the original, and that modern English should accept this. My academic hackles rise at this; I think it is a loss to the language. In terms of actual usage, of course, he is right. It is pointless to fight to hold back a change in language that the popular will has demanded.
But if your teacher is a pedant, do not use decimate to refer to any loss greater than a tenth.