1. Fundamental reasons; the basis.
2. An exposition of principles or reasons.

[Late Latin ratiōnāle, from neuter of Latin ratiōnālis, rational. See rational.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.