Derailleur gears several standards in use, and in each the product of the derailleur's actuation ratio and the length of cable pulled must equal the pitch of the rear sprockets. The following standards exist. Some rear derailleurs, especially for mountain bikes, incorporate a clutch to keep the lower length of chain in sufficient tension to prevent the chain from striking the bottom of the chain stay, called "chain slap", and which can damage the chain stay. Clutches are also helpful in preventing the chain from derailing from the chain ring on systems without a front derailleur. The front derailleur only has to
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