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
Names for the number 0 in English Names for the number 0 in English Zero is the usual name for the number 0 in English. In British English "nought" is also used. In American English "naught" is used occasionally for zero, but as with British English, "naught" is more often used as an archaic word for nothing. "Nil", "love", and "duck" are used by different sports for scores of zero. It is quite common in English to describe decades with a plural of the first year of the decade for example "the nineties" which can be written as "the 90s". There was a debate on what to