focuser

focus ► NOUN (pl. focuses or foci) 1) the centre of interest or activity. 2) the state or quality of having or producing clear visual definition: his face is out of focus. 3) the point at which an object must be situated with respect to a lens or mirror for an image of the object to be well defined. 4) a focal point. 5) an act of focusing on something. 6) the point of origin of an earthquake. Compare with EPICENTRE(Cf. ↑epicentre). 7) Geometry one of the fixed points from which the distances to any point of an ellipse, parabola, or other curve are connected by a linear relation.

► VERB (focused, focusing or focussed, focussing) 1) adapt to the prevailing level of light and become able to see clearly. 2) adjust the focus of (a telescope, camera, etc.). 3) (with reference to rays or waves) meet or cause to meet at a single point. 4) (focus on) pay particular attention to.

DERIVATIVES focuser noun.

ORIGIN Latin, 'domestic hearth' .