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 states like New-Brunswick, Quebec, Ivory Coast, Benin, Togo, Guinea, Cameroon, Congo, Democratic Republic of the Congo, Madagascar, Mauritius, Tchad, Djibouti, Senegal, Morocco, Algeria, Tunisia, Lebanon, France, Belgium, Switzerland, Luxembourg, Monaco, Aosta Valley, French Polynesia, New Caledonia, and Vanuatu adopting it as their official language. This geographical diversity has led to many different contacts with vernacular dialects, regional and international languages, from which French has often been enriched locally. In a number of countries and regions where French shares co-officiality with English (Cameroon, Canada, Jersey, Mauritius, Rwanda, Vanuatu), particular lexical regionalisms are observed where French and English terms are used interchangeably.