Choose the word which is different from the rest.

The answer is B. Diagonal.

An arc is a part of the circumference of a circle. A radius is a line segment from the center of a circle to any point on the circumference. A diameter is a line segment that passes through the center of a circle and has endpoints on the circumference. A tangent is a line that intersects a circle at exactly one point. A diagonal is a line segment that connects two non-consecutive vertices of a polygon.

In this question, all of the options except B are related to circles. A diagonal is not related to circles.