The following text is taken directly from the "ISAF Racing Rules of Sailing 2009-2012." Rule 18 is presented in full detail, along with all related definitions. The subject lines for related or referenced rules are also presented.


PART 1 FUNDAMENTAL RULES

PART 2 WHEN BOATS MEET

SECTION A - RIGHT OF WAY

13 WHILE TACKING

SECTION B - GENERAL LIMITATIONS

15 ACQUIRING RIGHT OF WAY
16 CHANGING COURSE

SECTION C - AT MARKS AND OBSTRUCTIONS

18 MARK-ROOM

18.1 When Rule 18 Applies

18.2 Giving Mark-Room

18.3 Tacking When Approaching a Mark

18.4 Gybing

18.5 Exoneration

Rule 19 ROOM TO PASS AN OBSTRUCTION
Rule 20 ROOM TO TACK AT AN OBSTRUCTION

SECTION D - OTHER RULES

Rule 22 CAPSIZED, ANCHORED OR AGROUND; RESCUING

PART 3 CONDUCT OF A RACE
Rule 28 SAILING THE COURSE
Rule 30 STARTING PENALTIES

PART 4 OTHER REQUIREMENTS WHEN RACING
Rule 44 PENALTIES AT THE TIME OF AN INCIDENT


DEFINITIONS

A term used as stated below is shown in italic type or, in preambles, in bold italic type.

Abandon A race that a race committee or protest committee abandons is void but may be resailed.

Clear Astern and Clear Ahead; Overlap One boat is clear astern of another when her hull and equipment in normal position are behind a line abeam from the aftermost point of the other boat’s hull and equipment in normal position. The other boat is clear ahead. They overlap when neither is clear astern. However, they also overlap when a boat between them overlaps both. These terms always apply to boats on the same tack. They do not apply to boats on opposite tacks unless rule 18 applies or both boats are sailing more than ninety degrees from the true wind.

Finish A boat finishes when any part of her hull, or crew or equipment in normal position, crosses the finishing line in the direction of the course from the last mark, either for the first time or after taking a penalty under rule 44.2 or, after correcting an error made at the finishing line, under rule 28.1.

Keep Clear One boat keeps clear of another if the other can sail her course with no need to take avoiding action and, when the boats are overlapped on the same tack, if the leeward boat can change course in both directions without immediately making contact with the windward boat.

Leeward and Windward A boat’s leeward side is the side that is or, when she is head to wind, was away from the wind. However, when sailing by the lee or directly downwind, her leeward side is the side on which her mainsail lies. The other side is her windward side. When two boats on the same tack overlap, the one on the leeward side of the other is the leeward boat. The other is the windward boat.

Mark An object the sailing instructions require a boat to leave on a specified side, and a race committee boat surrounded by navigable water from which the starting or finishing line extends. An anchor line or an object attached temporarily or accidentally to a mark is not part of it.

Mark-Room Room for a boat to sail to the mark, and then room to sail her proper course while at the mark. However, mark-room does not include room to tack unless the boat is overlapped to windward and on the inside of the boat required to give mark-room.

Obstruction An object that a boat could not pass without changing course substantially, if she were sailing directly towards it and one of her hull lengths from it. An object that can be safely passed on only one side and an area so designated by the sailing instructions are also obstructions. However, a boat racing is not an obstruction to other boats unless they are required to keep clear of her, give her room or mark-room or, if rule 22 applies, avoid her. A vessel under way, including a boat racing, is never a continuing obstruction.

Overlap See Clear Astern and Clear Ahead; Overlap.

Postpone A postponed race is delayed before its scheduled start but may be started or abandoned later.

Proper Course A course a boat would sail to finish as soon as possible in the absence of the other boats referred to in the rule using the term. A boat has no proper course before her starting signal.

Racing A boat is racing from her preparatory signal until she finishes and clears the finishing line and marks or retires, or until the race committee signals a general recall, postponement or abandonment.

Room The space a boat needs in the existing conditions while manoeuvring promptly in a seamanlike way.

Start A boat starts when, having been entirely on the pre-start side of the starting line at or after her starting signal, and having complied with rule 30.1 if it applies, any part of her hull, crew or equipment crosses the starting line in the direction of the first mark.

Tack, Starboard or Port A boat is on the tack, starboard or port, corresponding to her windward side.

Zone The area around a mark within a distance of three hull lengths of the boat nearer to it. A boat is in the zone when any part of her hull is in the zone.

Windward See Leeward and Windward