The luff, clew, and leech are all parts of a sail. The luff is the leading edge of a sail, the clew is the bottom back corner (farthest from the mast) and the leech is the bottom back edge. For a triangular sail, like the mainsail on a Bermuda-rigged sailboat, the leech would be the hypotenuse between the clew and the head of the sail. The luff runs along the mast from the head to the tack. Finally, the foot runs from the tack to the clew. In this case, "tack" refers to a sail part and not the side of the boat the wind is coming from while underway.

The origins of these terms date to antiquity and are mostly of Dutch and Middle-English origin reflecting the rich nautical history of these sea-faring nations. Moreover, the terms are common enough that sailors speaking different languages will know and understand their meaning.

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