Derailleur gears by 13 drive-train. Most road bicycles have two chainrings, and touring bicycles commonly have three. The rear derailleur serves double duty: moving the chain between rear sprockets and taking up chain slack caused by moving to a smaller sprocket at the rear or a smaller chainring by the front derailleur. In order to accomplish this second task, it is positioned in the path of the bottom, slack portion of chain. Sometimes the rear-derailleurs are re-purposed as chain tensioners for single-speed bicycles that cannot adjust chain tension by a different method. Although variations exist, as noted below, most rear derailleurs have
French corsairs of the French Crown, if captured by the enemy, they could in principle claim treatment as prisoners of war, instead of being considered pirates. Because corsairs gained a swashbuckling reputation, the word "corsair" is also used generically as a more romantic or flamboyant way of referring to privateers, or even to pirates. The Barbary pirates of North Africa as well as the Ottoman Empire were sometimes called "Turkish corsairs". The word "corsair" comes directly from the French word "corsaire", itself borrowed from the Italian "corsaro". This derives from the Latin "cursus", meaning "course" (as in journey or expedition). The French