A blade is a term often used to describe a basis entity in the space defined by a geometric algebra. Since a geometric algebra is a multi-graded space, the basis entities also have multiple grades. To distinguish the various graded entities, the blades are often prefixed by their grade. For example a grade- basis entity would be called a -blade.

The number of linearly independent -blades in a particular geometric algebra is dependent on the number of dimensions of the manifold on which the algebra is defined. For an -dimensional manifold, the number of -blades is given by the binomial coefficient.