There are 50 defined terms in "The Rules of Golf". These terms identify and clarify various parts of the golf course, items found on the course and people on the golf course. Throughout the Rule book (and in this article), the 50 defined terms appear in italics. The first step in answering a question on the Rules or in making a ruling is to know precisely who was involved and where the incident took place.
Consider the simple situation of a ball at rest moved. The title of Rule 18 is "Ball at Rest Moved", however, knowing who moved the ball will lead you to the correct sub-section of this Rule.
When a ball at rest has been moved by an outside agency, such as a spectator, animal, referee, player in another group, etc., Rule 18-1 applies. There is no penalty and the ball must be replaced.
Player, Partner, Caddie or Equipment
The term "player" is not defined in the Rules, however, it is important to know when a partner is involved, who the caddie is and to whom the equipment belongs, especially when a golf cart is shared by two or more players. Rule 18-2a applies when a ball at rest has been moved by the player, his partner, either of their caddies or their equipment causes the ball to move.
Like the term "player", the Rules do not provide a definition for "opponent." However, this term is used only in match play. When a ball at rest has been moved by an opponent or his caddie or equipment Rule 18-3 applies.
Fellow-Competitor Rule 18-4 applies when a ball at rest has been moved by a fellow-competitor, his caddie or his equipment. In this case there is no penalty and the ball must be replaced.
Another example that illustrates why the "Definitions" are important is in removing a loose impediment. Depending on the location of where the incident took place, the resulting answer may vary.
When the ball lies on the teeing ground, there is no penalty for removing a loose impediment even if the ball moves, as the player does not have a ball in play.
Through the Green
Loose impediments which lie through the green may be removed without penalty, however if the ball moves as a direct result of removing the loose impediment, the player incurs a penalty of one stroke and must replace the ball.
When the ball and the loose impediment lie in or touch the same hazard, the loose impediment must not be touched or removed. If the player does so, he incurs the general penalty, which is loss of hole in match play or two strokes in stroke play.
A player may remove a loose impediment when the ball lies on the putting green. In this case if the ball moves, there is no penalty provided the movement of the ball was a direct result of the removal of the loose impediment.
As you can see, the person involved or the simple location of the golf ball will result in quite different answers.
The Rules staff at the USGA answers over 20,000 inquiries on the Rules of Golf each year. Oftentimes these questions can be answered simply by referencing the "Definitions". One good way to learn the definitions is to make a set of flash cards and quiz yourself on a regular basis. Knowing the definitions truly are the foundation to learning the Rules of Golf and with a good knowledge of the definitions, you will be able to build on other aspects of the Rules and answer many other questions.
Reprinted with permission from the USGA.