cat·e·nary /ˈkætəˌnɛri, ||kəˈtinəri/
  鏈,懸鏈線,垂曲線(a.)垂曲線的
  Cat·e·na·ry Cat·e·na·ri·an a.  Relating to a chain; like a chain; as, a catenary curve.
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  Cat·e·na·ry, n.; pl. Catenaries  Geol. The curve formed by a rope or chain of uniform density and perfect flexibility, hanging freely between two points of suspension, not in the same vertical line.
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  catenary
       n : the curve theoretically assumed by a perfectly flexible and
           inextensible cord of uniform density and cross section
           hanging freely from two fixed points