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Glite Dictionary
🙁 An unwanted person 🛺 A turning part 🛞 A spare tire
fifth wheel

fifth wheel

1 9.1
A metal part on a wagon that lets the front axle turn for steering
  • noun
  • /ˈfɪfθ wiːl/
  • Archaic
translation icon : quinta rueda (mecánica)
  • The horse-drawn wagon moved smoothly because its fifth wheel allowed easy steering.

Examples

  • When I raised the subject once, his eyes darkened; he walked off to grease the fifth wheel on his wagon.

    Fiction book (2002)

  • He adjusted the fifth wheel to ensure the wagon turned properly around the corner.

  • The mechanic showed how the fifth wheel operates to enable the wagon to pivot easily.

Surface Forms

fifth wheel singular
fifth wheels plural

Morphology

fifth + wheel

The compound transparently combines 'fifth' (an ordinal) and 'wheel' (a rotating device), so a B1 learner could infer it refers to a particular or additional wheel. However, the specific technical sense—a horizontal bearing above the front axle that enables pivoting—is a specialized mechanical function not directly predictable from the constituents, so full understanding requires prior exposure or explanation.

Etymology

Fifth wheel originally referred to a horizontal wheel placed above the front axle of early wagons so the front could 'turn'. Because it let the wagon change direction, this 'fifth' wheel was the moving part that made steering possible.