Penalty Stroke
The penalty stroke is the stroke added to your score for a breach of the rules.
The penalty stroke is the currency of the rulebook. It is added to your stroke count without you having played a ball. The most common cases on the course: ball in the water hazard dropped, ball declared unplayable, ball lost or in out of bounds. Most situations cost one penalty stroke, some two, such as playing a wrong ball in stroke play. The rulebook of the R&A and the USGA regulates every case exactly.
In practice it is always about the correct procedure after the breach. An example: your ball lands in the pond, marked red. You drop within two club lengths of the entry point, count the stroke into the water, the penalty stroke, and play on. Your third stroke therefore becomes the fourth. Honest counting is what matters: nobody but you sees every ball. The rulebook lives on self-reporting, that distinguishes golf from almost all other sports.
A typical mistake is playing on without clarification. Whoever drops wrongly or chooses the wrong option collects further penalty strokes. If in doubt ask your fellow players or play under Rule 3-3 with two balls and clarify it at the club office. You can find the basics in the FAQs and under the term free drop, the legal counterpart without penalty.
FAQ
How many penalty strokes does which breach of the rules cost?
Most everyday situations cost you exactly one penalty stroke, such as the ball in the penalty area, a lost ball or when you declare your ball unplayable. Two penalty strokes apply for more serious errors, such as playing a wrong ball in stroke play or playing from the wrong place. Anyone who signs their scorecard incorrectly even risks disqualification in a tournament.
What do I do if I am unsure about a rule?
In stroke play you may play two balls under Rule 3.3 and have the situation clarified later at the club office before you hand in your scorecard. Tell your fellow players beforehand which ball you want to have counted, in case the rule allows it. In casual play it is enough to ask the fellow players and do it right the next time.
What is the difference between a penalty stroke and a free drop?
In the free drop you drop without penalty because the course gives you relief from the ball, for example at paths, puddles or animal holes. In the penalty stroke you pay one stroke extra because you want out of a difficult situation that belongs to the game. You can find the details of the legal escape without penalty at the free drop.