Circle segments are true circular arcs defined by exactly three points. The first two points are the ends of the arc and the third point will lie on the interior of the arc between the first two (2 Points & Shoulder). Alternatively, the third point can define the center of the circle. Change the role of the third point using the commands in the Circle Segment Options frame. Select 2 Points & Center to have the third point define the center point.
You can also use a sweep angle to define a circular arc. Select 2 Points & Angle in the Circle Segment Options frame and enter the sweep Angle in the text field. Define the two end points of the arc as before. The appropriate arc will be generated necessary to sweep the input angle between the two arc endpoints. Use Flip to reverse the arc if necessary. Or you can use Point, Center, & Angle to specify first a point on the arc, then the center point of the arc and enter the angle swept by this radius in the Angle field. Again, use Flip to reverse the arc if necessary.
Tip: Circle segments are particularly well suited to creating cylindrical or spherical far field topology.