The infinitesimal algebraic object associated with a Lie Groupoid. A Lie algebroid over a Manifold is a Vector Bundle over with a Lie Algebra structure (Lie Bracket) on its Space of smooth sections together with its Anchor .
See also Lie Algebra
References
Weinstein, A. ``Groupoids: Unifying Internal and External Symmetry.'' Not. Amer. Math. Soc. 43,
744-752, 1996.