English
subdiagonal
From sub- + diagonal.
Today it means
adj Said of an entry of a square matrix: that it lies anywhere in the lower triangular area below the main diagonal of the matrix.
Sources
Sources: Wiktionary, “subdiagonal”. By Wiktionary contributors, CC BY-SA 4.0, via kaikki.org (dump of Oct 3 2026); text adapted and restructured. Language periods are conventional ranges, not dates for this word. License.
Etymograph / subdiagonal