Circle
The Circle primitive is a closed circular Bezier or Spline curve. The Bezier type is equivalent to a curve made by the Bezier tool. The Spline type is a Hermite Cubic spline, equivalent to that made by the Adding Curves tool.
Note: You can fill the shape using the Curve Fill tool.
Circle Properties
Circle 

Enable 
Toggles the primitive. 
Type 
Selects the curve type: • Bezier  Draw using Bezier control points. • Spline  Draw using Hermite Cubic spline type. This locates all vertices along the path of the circle. 
Position X, Y 
Determines the X, Y position along the plane defined by Axis. 
Radius 
Sets the circle radius. 
Axis 
Chooses the plane on which to draw the circle: • X  Align to the YZ plane. • Y  Align to the XZ plane. • Z  Align to the XY plane. 