Leeward is the direction downwind from the point of reference. The side of the ship towards the leeward is its lee side. If the vessel is heeling under the pressure of the wind, this will be the "lower side".
The traditional nautical pronunciations are the elided forms /'lju:ɚd/ or /'lu:ɚd/ (also /lɪʊɚd/, /lʊɚd/), and /'wɪndɚd/. However, nowadays these are sometimes regarded as old-fashioned, and the more literal /'li:wɚd/ and /'wɪndwɚd/ are common. The pronunciation for the Leeward and Windward Islands and the Leeward Antilles is normally the latter form.
In the case of an archipelago, "windward islands" are upwind and "leeward islands" are the downwind ones.
"Downwind" has specific connotations in industrial cities in the English North, where less desirable or expensive housing was often situated to the leeward of steelworks, blast furnaces, mills or other sources of intense pollution. Hence in some cities it is used as a generic, slang, pejorative and discriminatory term for less wealthy areas or their inhabitants.
Windward and leeward directions are important factors to consider when sailing a sailing ship - see points of sail. Other terms with broadly the same meaning are widely used, particularly "upwind" and "downwind", and many variations using the metaphor of height ("come up", "drop down", "we're pointing higher than them" "head below that mark", and so on).
The windward vessel is normally the more maneuverable vessel. For this reason, rule 12 of the International Regulations for Preventing Collisions at Sea stipulate that the leeward vessel has right of way over the windward vessel. Similarly, a square rigged warship would often try to enter battle from the windward direction (or "hold the weather gauge"), thus gaining an important tactical advantage over the opposing warship – the warship to windward could choose when to engage and when to withdraw. The opposing warship to leeward could often do little but comply without exposing itself unduly. This was particularly important once artillery was introduced to naval warfare. The ships heeled away from the wind so that the leeward vessel was exposing part of her bottom to shot. If damaged between wind and water, she was consequently in danger of sinking when on the other tack. See Spanish Armada.
The term "lee" derives from Old English hleo, "shelter", and was in use at least as early as 900 C.E.