Centre

• In exact sciences, the centre of a circle is the point which is the same distance from every point on the circumference. It is the point on which the fixed leg of a pair of compasses is placed to allow the other leg, which holds the pencil, to draw the circle. So those who make technical drawings, etc, centre a circle on a particular point.

• In academic English, to say centre round something is regarded as inaccurate. You can 'have a discussion round a point', or you can (with a strong connotation of irrelevance) 'talk round the issue'; but you should 'have a discussion centred on a particular subject'.

See also focus.