## Tuesday, 22 July 2014

### Parameter

What has happened to the powerful mathematical word 'parameter'? More and more we hear people, particularly those engaged in management speak, who clearly have not a clue as to what the word really means, and using to it to mean 'perimeter'! So they talk about 'having to work with certain parameters', meaning within certain boundaries. This has become so commonplace that some dictionaries seem to have conceded this as a secondary meaning. This is all very irritating to a mathematician! Either leave our concepts alone please or use them properly!

Parameters are not things that you work within. The word is a mathematical term for what is sometimes called, enigmatically, a variable constant. To take a simple example, the equation y = mx is the general form of the equation for a straight line passing through the origin. The x and y are the independent and dependent variables, respectively. But m represents the slope of the line. For any given line, it is a constant. But m can take any value, so it is also a variable. So the value it takes determines which straight line through the origin is being considered. This m is a therefore a parameter.

If you want to transfer this idea to a business or social context, then you could say that the parameters are the variables whose values determine precisely the nature of the situation you are in. It would be perfectly acceptable, for example, to say that 'two of the the parameters for an architectural project are budget and completion time'. But not to say that 'the parameters of the site are clearly marked on this map'. That's talking about perimeter!