**Q: **Is a circle a simple closed shape in Euclidean geometry? ¶

**A: **Yes.

**Q: **Is a circle an ellipse with an eccentricity of zero? ¶

**A: **Yes, and meaning that the two foci coincide with each other as the centre of the circle.

**Q: **Is a circle a highly symmetric shape: every line through the centre forms a line of reflection symmetry and it has rotational symmetry around the centre for every angle? ¶

**A: **Yes.

**Q: **Is a circle sometimes said to be drawn about two points? ¶

**A: **Yes.

**Q: **Is a circle the basis for the wheel? ¶

**A: **Yes, and which, with related inventions such as gears, makes much of modern machinery possible.

**Q: **Is a circle also a different special case of a Cartesian oval in which one of the weights is zero? ¶

**A: **Yes.

**Q: **Is a circle the shape with the largest area for a given length of perimeter? ¶

**A: **Yes.

**Q: **Are circles actually circles: a generalised circle is either a circle or a line? ¶

**A: **Yes.

**Q: **Is a circle subtended by the same chord and on the same side of the chord? ¶

**A: **Yes, and then the central angle is twice the inscribed angle.

**Q: **Is a circle the plane curve enclosing the maximum area for a given arc length? ¶

**A: **Yes.

**Q: **Is a circle only the boundary and the whole figure is called a disc? ¶

**A: **Yes.

**Q: **Is a circle the problem? ¶

**A: **Yes, and proposed by ancient geometers, of constructing a square with the same area as a given circle by using only a finite number of steps with compass and straightedge.

**Q: **Is a circle a tangent to the circle? ¶

**A: **Yes.

**Q: **Is a circle a plane figure bounded by one line? ¶

**A: **Yes, and such that all right lines drawn from a certain point within it to the bounding line, are equal.

**Q: **Is a circle a simple closed curve which divides the plane into two regions: an interior and an exterior? ¶

**A: **Yes.

**Q: **Is a circle the simplest example of this type of figure? ¶

**A: **Yes.

**Q: **Are circles similar? ¶

**A: **Yes.