Definitions:
the centre of interest or activity

the state or quality of having or producing clear visual definition

one of the fixed points from which the distances to any point of a given curve, such as an ellipse or parabola, are connected by a linear relation.

an element of a sentence that is given prominence by intonational or other means.

adapt to the prevailing level of light and become able to see clearly

pay particular attention to

place the focus on (an element of a sentence).