A curved surface on which all points are the same distance from the center is called a sphere.
circle
This is the center, or locus, of a set of points, such as a curve or circle.
A circle
"Radius" is a measurement that refers to a circle. It's the distance from the circle's center to any point on its curve.
... is called a Great Circle arc.
A circle.
The spelling "radios" is the plural of "radio."The geometry term radius is the distance from a circle (or sphere surface, or curve) to its center.
circle
This is the center, or locus, of a set of points, such as a curve or circle.
The distance from the fixed point at the center of a circle to any point on the curve is called the radius.
An imaginary line that follows the curve of the Earth is called a great circle. It represents the shortest distance between two points on the Earth's surface and is often used in navigation and mapping.
A circle
Since the surface of water rises up to the sides of the cylinder, the low point is in the center of the surface. (Volume is assumed unless boiling or melting points are stated)
Actually, this turns out to be more of a debate than you might think. Historically, most of us were taught the shortest distance between two points is a straight line; that is a principle of Euclid's geometry. But not everyone agrees with Euclid, and there are other types of geometry. For example, because the Earth is a sphere, and not flat as distance maps portray it, that is why some scientists say that the shortest distance is actually a sphere or a curve (in other words, the distance would be measured by following the Earth's contours).
Diameter is the length of a straight line passing through the center of a circle or sphere and connecting two points on the circumference of the circle or the surface of the sphere. Circumference is the length of the closed curve of a circle.
Points on the Curve was created on 1984-01-16.
That refers to the center of the circle that "fits best" - that follows the direction of a curve (locally) most closely. (The formal definition, of course, is a bit more complicated, and involves concepts of calculus, such as limits.)