Straight line
Given a straight line (a directrix) and a point (the focus) which is not on that line, a parabola is locus of all points whose distance form the directrix is the same as its distance from the focus.
parabola
A circle
This is the definition of a circle.
Straight line
A locus of points is just the set of points satisfying a given condition. The locus of points equidistant from a point is a circle, since a circle is just a set of points which are all the same distance away from the center
are the same distance from two points... Apex - TF
Given a straight line (a directrix) and a point (the focus) which is not on that line, a parabola is locus of all points whose distance form the directrix is the same as its distance from the focus.
parabola
The center isn't the locus, and a point on the circumference isn't the locus.The whole circumference of the circle is the locus.It's the locus of all points that have the same distance from the center of the circle.
It is the locus of all points such that their distance from a fixed line (the directrix) is the same as their distance from a fixed point which is not on that line (the focus).
It can allow you to define shapes but that is not quite the same thing as an object.
The locus of points where the potential due to an isolated point charge is constant is a spherical surface centered on the point charge. This is because the potential decreases with distance from the point charge, so points at the same distance will have the same potential.
A circle
The set of all points a given distance from a center point is a circle. The given distance is the radius, and the given point is the center. Or, in 3 dimensional space, a sphere.
The set of all points in space that are the same distance from a given point is called a sphere.