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rule of the road

n. often pl. rules of the road

1. A set of customary practices, especially for the operation of a motor vehicle, boat, or aircraft, established to promote efficiency and safety.

2. A set of established rules or practices, usually unstated, intended to minimize confusion or conflict: "Great powers ... wishing to avoid war could resort to one of three tools: condominium, spheres of influence or rules of the road" (Charles William Maynes).

Indo-European & Semitic Roots Appendices

Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

Indo-European Roots

Semitic Roots

The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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