Tandem (or in tandem) is an arrangement where a team of machines, animals or people are lined up one behind another, all facing in the same direction. Tandem harness (the original use of the term in English) is used for two or more draft horses harnessed in a single line one behind another, as opposed to a pair, harnessed side-by-side, or a team of several pairs. Tandem harness allows additional animals to provide pulling power for a vehicle designed for a single animal.
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tandem A bicycle with two seats, two sets of pedals, and two wheels.