Circles: Special Segments in Circles

Tangents

The term 'tangent' comes from the Latin word 'tangere', which means 'to touch'.  A tangent line or line segment touches the circle in just one point, called the point of tangency.

 

Take a look at the circle below.

Circle with tangent line AB, tangent ray PQ and tangent segment XY
Circle with Tangents

Notice that lines AB, PQ, and XY all touch the circle in just one point.  All three of these are called tangents.  The points of tangency are A, P and X, respectively.