A special class of Fiber Bundle in which the Fiber is a Vector Space. Technically, a little more is required; namely, if is a Bundle with Fiber , to be a vector bundle, all of the Fibers for need to have a coherent Vector Space structure. One way to say this is that the ``trivializations'' , are Fiber-for-Fiber Vector Space Isomorphisms.
See also Bundle, Fiber, Fiber Bundle, Lie Algebroid, Stable Equivalence, Tangent Map, Vector Space, Whitney Sum