Any technique used in medical diagnosis. / (computing) Any tool or technique used to find the root of a problem. / That by which anything is known; a symptom.

Abbreviation of diagnosis. / Abbreviation of diagram.

Abbreviation of diagnostic.

(linear algebra) An element on the main diagonal of a square matrix, that is, an element in row k and column k where k is an integer between 1 and the number of rows (or columns) in the matrix.

(linear algebra) A main diagonal.

(linear algebra) The entries of a square matrix from the top left to the bottom right.

(linear algebra) A matrix in which the entries outside the main diagonal are all zero.

One who keeps a diary.

(set theory) A diagram representing some sets by contours of closed shapes, such as circles or ellipses (and sometimes also the universal set as a rectangle enclosing all of these shapes), and indicating the relationships between the sets: by overlapping the shapes to show that the corresponding sets have a non-empty intersection, and by possibly (but not necessarily) enclosing all of the sets (which are proper subsets of the universal set) within a universal set (represented typically by a rectangle); such that the total number of simply connected regions is 2ⁿ, where n is the number of depicted sets which are proper subsets of the universal set.

(historical) The dispersion of the Jews among the Gentiles after the Babylonian captivity (6th century BCE). / (by extension) Any similar dispersion.