In linear algebra and functional analysis, a projection is a linear transformation P from a vector space to itself such that P2 = P. Projections map the whole vector space to a subspace and leave the points in that subspace unchanged.
Though abstract, this definition of "projection" formalizes and generalizes the idea of graphical projection. One can also consider the effect of a projection on a geometrical object by examining the effect of the projection on points in the object.