Definition:Echelon Matrix/Echelon Form/Non-Unity Variant/Definition 1
Definition
Let $\mathbf A = \sqbrk a_{m n}$ be a matrix whose order is $m \times n$.
$\mathbf A$ is in non-unity echelon form if and only if:
- $(1): \quad$ Each row (except perhaps row $1$) starts with a sequence of zeroes
- $(2): \quad$ Except when for row $k$ and row $k + 1$ are zero rows, the number of zeroes in this initial sequence in row $k + 1$ is strictly greater than the number of zeroes in this initial sequence in row $k$
- $(3): \quad$ The non-zero rows appear before any zero rows.
Also known as
An echelon matrix and a matrix in echelon form are the same thing.
A matrix in echelon form is also sometimes seen as being in row echelon form.
The definition of column echelon form is directly analogous.
Also defined as
Many sources require that, for a matrix to be in echelon form, the leading coefficient in each non-zero row must be $1$.
Such a matrix is detailed in Echelon Matrix.
Also see
- Results about echelon matrices can be found here.
Linguistic Note
An echelon is:
- a formation of troops, ships, aircraft, or vehicles in parallel rows with the end of each row projecting further than the one in front.
It derives from the French word échelon, which means a rung of a ladder, which describes the shape that this formation has when viewed from above or below.
It is pronounced e-shell-on or something like ay-shell-on, where the first ay is properly the French é.
Avoid the pronunciation et-chell-on, which is technically incorrect.
Sources
- 1998: Richard Kaye and Robert Wilson: Linear Algebra ... (previous) ... (next): Part $\text I$: Matrices and vector spaces: $1$ Matrices: $1.5$ Row and column operations