\begin{definition}[Definition:Matrix/Row]
Let $\mathbf A$ be an $m \times n$ matrix.
For each $i \in \closedint 1 m$, the '''rows''' of $\mathbf A$ are the ordered $n$-tuples:
:$r_i = \tuple {a_{i 1}, a_{i 2}, \ldots, a_{i n} }$
where $r_i$ is called the '''$i$th row of $\mathbf A$'''.
A '''row''' of an $m \times n$ matrix can also be treated as a $1 \times n$ row matrix in its own right:
:$r_i = \begin {bmatrix} a_{i 1} & a_{i 2} & \cdots & a_{i n} \end {bmatrix}$
for $i = 1, 2, \ldots, m$.
\end{definition}