Definition: Relief Area

The area where a player must drop a ball when taking relief under a Rule. With the exception of back-on-the-line relief (see Rules 16.1c(2), 17.1d(2), 19.2b and 19.3), each relief Rule requires the player to use a specific relief area whose size and location are based on these three factors:

Reference Point: The point from which the size of relief area is measured.
Size of Relief Area Measured from Reference Point: The relief area is either one or two club-lengths from the reference point, but with certain limits:
Limits on Location of Relief Area: The location of the relief area may be limited in one or more ways so that, for example:

It is only in certain defined areas of the course, such as only in the general area, or not in a bunker or a penalty area,
It is not nearer the hole than the reference point or must be outside a penalty area or a bunker from which relief is being taken, or
It is where there is no interference (as defined in the particular Rule) from the condition from which relief is being taken.

With back-on-the-line relief, the player must drop on the line in a location allowed by the Rule being used and the spot where the ball first touches the ground when dropped creates a relief area that is one club-length in any direction from that point.

When a player is required to drop again or for a second time using back-on-the-line relief, the player may:

Change the spot on which the ball is dropped (such as dropping nearer to or farther from the hole), and the relief area changes based on that point, and
Drop in a different area of the course.

But doing so does not change how Rule 14.3c applies.

In using club-lengths to determine the size of a relief area, the player may measure directly across a ditch, hole or similar thing, and directly across or through an object (such as a tree, fence, wall, tunnel, drain or sprinkler head), but is not allowed to measure through ground that naturally slopes up and down.

See Committee Procedures, Section 2I (Committee may choose to allow or require the player to use a dropping zone as a relief area when taking certain relief).

[+] Relief Area/1 – Determining Whether Ball Is in Relief Area (New)