lay line - The course that will take a close hauled boat around the next mark.

lee - The side of the boat away from the wind.

leech - The back edge of the sail.

leeward - Away from the wind.

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 tack overlap, the one on the leeward side of the other is the leeward boat.  The other is the windward boat. (ISAF Rules)

leg - The course between two buoys of a race.

luff - The front edge of the sail.

luffing - Flapping in the sail.

luffing rights - Your right to force a boat passing to windward to go up into the wind until she is head to wind.

main sheet - The rope which pulls the main sail in.

mark - A buoy or other object which helps determine the race course.

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

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. (ISAF Rules)

mast - A pole to which a sail is attached.

Obstruction - An object that a boat could not pass without changing course substantially, if she were sailing directly towards it and one of her hulls lengths from it.  An object that can be safely passed on only one side and an area so designated by the sailing instruction 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 underway, including a boat racing, is never a continuing obstruction. (ISAF Rules)

ooching - sudden forward body movement, stopped suddenly (42.2 c)

outhaul - A rope at the end of a boom or at the top of the sail which tightens the sail.

overlap - When some part of one boat is beside another boat.

Overlap - See Clear Astern and Clear Ahead; Overlap (ISAF Rules)

overtaking boat - A boat getting closer to the boat in front of it.