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
A Dictionary of the English Language all words which we use in the English tung...into one dictionary..." In 1598 an Italian–English dictionary by John Florio was published. It was the first English dictionary to use quotations ("illustrations") to give meaning to the word; in none of these dictionaries so far were there any actual definitions of words. This was to change, to a small extent, in schoolmaster Robert Cawdrey's "Table Alphabeticall", published in 1604. Though it contained only 2,449 words, and no word beginning with the letters "W", "X", or "Y", this was the first monolingual English dictionary. Several more dictionaries followed: in Latin, English, French