The curve described by a point which moves under given condition or conditions is called its locus.

`text(Note : Steps to find locus of a point.)`

`text(Step I :)` Assume the coordinates of the point say `(h, k)` whose locus is to be determined.

`text(Step II :)` Write the given condition in mathematical form involving `h, k`.

`text(Step III :)` Eliminate the variable `(s)`, if any.

`text(Step IV : )` Replace `h` by `x` and `k` by `y` in the result obtained in step `III.`

The equation so obtained is the locus of the point which moves under some condition `(s)`.