Definition of «arrowroot»

Arrowroot is a type of powder that comes from the roots of a tropical plant, and it is often used as a thickening agent in cooking.

I have substituted tapioca flour for arrowroot powder in many recipes and has worked well. (elanaspantry.com)
Can I substitute flour with arrowroot flour or gluten free flour using the same amount or will it be dry? (simplyrecipes.com)
And would potato starch be a substitute for arrowroot powder and tapioca powder? (paleorunningmomma.com)
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