\begin{matrix}
a & b & c \\
d & e & f \\
g & h & i
\end{matrix}
matrix
\begin{pmatrix}
a & b & c \\
d & e & f \\
g & h & i
\end{pmatrix}
matrix (parentheses)
\begin{bmatrix}
a & b & c \\
d & e & f \\
g & h & i
\end{bmatrix}
matrix (brackets)
\begin{Bmatrix}
a & b & c \\
d & e & f \\
g & h & i
\end{Bmatrix}
matrix (braces)
\begin{vmatrix}
a & b & c \\
d & e & f \\
g & h & i
\end{vmatrix}
matrix (verts)
\begin{Vmatrix}
a & b & c \\
d & e & f \\
g & h & i
\end{Vmatrix}
matrix (double verts)
A_{m,n} =
\begin{pmatrix}
a_{1,1} & a_{1,2} & \cdots & a_{1,n} \\
a_{2,1} & a_{2,2} & \cdots & a_{2,n} \\
\vdots & \vdots & \ddots & \vdots \\
a_{m,1} & a_{m,2} & \cdots & a_{m,n}
\end{pmatrix}
A_{m,n} =
\begin{pmatrix}
a_{1,1} & a_{1,2} & \cdots & a_{1,n} \\
a_{2,1} & a_{2,2} & \cdots & a_{2,n} \\
\vdots & \vdots & \ddots & \vdots \\
a_{m,1} & a_{m,2} & \cdots & a_{m,n}
\end{pmatrix} arbitrarily sized matrix with dots
n \cdot (
\begin{smallmatrix}
a & b\\
c & d
\end{smallmatrix}
)
small matrix
\begin{array}{l|r}
20 & -30\\
30 & -40
\end{array}
array
\left|
\begin{array}{ccc}
1 & 2 & 3\\
4 & 5 & 6\\
7 & 8 & 9
\end{array}
\right|
determinant