Mittediagonaalsed

Mittediagonaalsed is an Estonian adjective meaning not diagonal, used to describe objects or structures that do not conform to a diagonal arrangement or orientation. The word is formed from the negating prefix mitte- and the plural adjective diagonaalsed (diagonal), and it is commonly written as a hyphenated compound in standard usage, though some texts spell it without a hyphen.

In mathematics, the term is most often applied to matrices. A matrix is described as mitte-diagonaalne if it has nonzero elements outside the main diagonal, i.e., there exists an off-diagonal entry aij with i ≠ j. Equivalently, such a matrix is not a diagonal matrix, which would have all off-diagonal entries equal to zero. The concept helps distinguish between diagonal and non-diagonal structures, with diagonal matrices typically bearing simpler properties in linear algebra.

Beyond matrices, mitte-diagonaalsed can be used in other contexts to indicate non-diagonal arrangements in grids, graphs, or layouts where the primary alignment follows or lies along the diagonal. The term emphasizes deviation from a diagonal form rather than being confined to a single mathematical object.

See also: diagonals, diagonal matrix, diagonalization. In practice, when writing in Estonian, prefer the hyphenated form “mitte-diagonaalsed,” though the non-hyphenated variant may appear in older or less formal texts.