(number theory) A deficient number.

(grammar) A verb with an incomplete conjugation; for example, one that can only be conjugated in certain persons and numbers.

(business, of an item) Upon receipt, damaged or defective to the point of being unusable.

(medicine) Any of several medical disorders that are present at birth.

(physics) the difference between the mass of an atom and the sum of the masses of its individual components in the free state; equivalent to the binding energy

(linear algebra) A square (n×n) matrix that has fewer than n linearly independent eigenvectors, and is therefore not diagonalisable.

plural of defective matrix

(geometry, non-Euclidean geometry) The amount by which the total of the interior angles of a triangle is less than 180° (π radians); the amount by which the total of the internal angles of a polygon is less than what would be expected on the Euclidean plane.

plural of defective number

(law) A problem with the chain of title to a parcel of real property that exposes the putative owner of the property to a potential legal dispute over the ownership of the property.