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To understand the principle of Peaucellier's link-work, it is convenient to consider previously certain properties of a linkage, (to coin a new and useful word of general application), consisting of an arrangement of six links, obtained in the following manner ... (etc.). ["Recent Discoveries in Mechanical Conservation of Motion," in "Van Nostrand's Eclectic Engineering Magazine," vol. XI, July-December 1874]
linkage link·age (lĭng'kĭj)
An association between two or more genes such that the traits they control tend to be inherited together.