caus·al /ˈkɔzəl/
  (a.)原因的,因果關係的,表示原因或理由的表示原因的詞
  Caus·al a.  Relating to a cause or causes; inplying or containing a cause or causes; expressing a cause; causative.
     Causal propositions are where two propositions are joined by causal words.   --Watts.
  Caus·al, n. A causal word or form of speech.
     Anglo-Saxon drencan to drench, causal of Anglo-Saxon drincan to drink.   --Skeat.
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  causal
       adj : involving or constituting a cause; causing; "a causal
             relationship between scarcity and higher prices"