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
Word sort Word sort A word sort is a developmental word study activity espoused by the "Words Their Way" curriculum as written by Donald R. Bear, Marcia Invernizzi, Shane Templeton, and Francine Johnston. The activity focuses students' attention on critical features of words, namely sound, pattern, and meaning. Recent descriptions of comprehensive vocabulary programs identify fostering word consciousness (getting students really interested in and excited about words) as a crucial component of effective programs. Word sorts are a method to foster word consciousness. The process of sorting words into various categories is the heart of word study. By categorizing different words by