What is a crossbow arrow called other than a bolt?

A quarrel or bolt is the term for the ammunition used in a crossbow. The name "quarrel" is derived from the French carré, "square", referring to the fact that they typically have square heads. They are typically shorter than traditional arrows, though some may be longer, and can be fired repetitively in some cases. Bolts and arrows have different flight characteristics. Bolts fall at the same rate, independent of the speed of flight. Arrows, in contrast, depend on gaining lift in flight, and hence have their centre of balance at a point about 9% of their length forward of their center. This is called "point planing".