Arrow

n. long thin weapon shot by a bow; symbol in the shape of an arrow

An arrow is a pointed projectile that is shot with a bow. It predates recorded history and is common to most cultures.
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Noun
1. a mark to indicate a direction or relation
(synonym) pointer
(hypernym) mark
(part-meronym) shaft
2. a projectile with a straight thin shaft and an arrowhead on one end and stabilizing vanes on the other; intended to be shot from a bow
(hypernym) projectile, missile
(hyponym) broad arrow
(part-holonym) bow and arrow
(part-meronym) arrowhead

(n.)
A missile weapon of offense, slender, pointed, and usually feathered and barbed, to be shot from a bow.
  

An element in a path diagram used to indicate causal flow from one variable to another, or, in narrower interpretation, to show which of two variables in a linear equation is the independent variable and which is the dependent variable.