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
Influence of French on English Influence of French on English There has been a long-standing influence of French on English, in terms of syntax, grammar, lexicon, spelling and pronunciation. Most French vocabulary that entered English occurred after the Norman conquest of England in 1066 and the establishment of a French-speaking administration. French became the language of the court, the administration and the elites for several centuries, until after the Hundred Years War. English has been constantly influenced by French from that time till present day. According to Laura K. Lawless, more than a third of the current English vocabulary is of French origin. According to