Is a circle a sphere?
A circle is two dimensional whereas a sphere is three dimensional, so they are different things. Any two dimensional section or slice of a sphere is a circle, however.
A sphere is a three dimentional shape, a circle is a two dimentional shape. You can't pick up a circle, it can only be drawn. In differential geometry, a one dimensional sphere is a point, a two dimensional sphere is a circle and a three dimensional sphere is what we call a "sphere", there is no limit to the number of dimensions a sphere can have.
Much bigger and better than a regular circle... But seriously, a great circle on a sphere is a circle that runs along the surface of that sphere and cuts it into two equal halves. It is the largest circle that can be drawn on a given sphere. The center of any great circle is the center of the sphere.
That's called a "great circle" of the sphere. -- It's any circle whose center is at the center of the sphere. -- Its diameter is equal to the diameter of the sphere. -- Its area is equal to 1/4 the surface area of the sphere. -- The shortest distance between any two points on the sphere is along the piece of the great circle on which they lie. (There's only one, unless the two points…
A great circle is a circle on the surface of a sphere whose center is at the center of the sphere. The shortest distance between two points on the surface of a sphere (like the Earth for example) is the piece of the great circle that joins them. If you're flying, then that's the route you want to follow.
The great circle is the intersection of a sphere and any plane passing through its centre. Given two distinct points on the surface of a sphere, those two points and the centre of the sphere define a plane. [If one of the points is at the antipodes of the other, an infinite number of planes are defined.] The great circle is the circle formed when that plane meets the surface of the sphere.