derailleur
UK[dɪˈreɪlə]US[dɪˈreɪlər]
n
a mechanism on a bicycle that moves the chain from one gear wheel to another.
Morpheme Breakdown
de
rail
eur
de
off, away
rail
rail, track
eur
agent or instrument
Etymology
the word 'derailleur' is a direct borrowing from modern french, where it functions as a noun meaning 'derailer' or 'device that moves something off its track'. it is constructed from the french verb 'dérailler', meaning 'to derail', which itself combines the prefix 'dé-' (from latin 'de-', indicating removal) and 'rail' (meaning track). the literal sense of a device that forces something off its rails was applied metaphorically to the bicycle component, which shifts the chain off one gear wheel and onto another. the suffix '-eur' is a typical french agentive suffix, here denoting the instrument that performs the action.
Analysis
Structure: de + rail + eur
de- (latin origin, meaning 'off, away'); rail (french origin, meaning 'rail, track'); -eur (french suffix, meaning 'agent or instrument').
Examples
he adjusted the derailleur to get a smoother gear change.
a high-quality derailleur is essential for precise shifting on mountain trails.
the mechanic explained that the problem was with the rear derailleur cable.