A vertical ellipsis symbol indicating omitted terms in a vertical sequence or matrix notation.
Examples
Vertical ellipsis in a matrix
\begin{pmatrix} a_{1,1} & a_{1,2} \\ a_{2,1} & a_{2,2} \\ \vdots & \vdots \\ a_{n,1} & a_{n,2} \end{pmatrix}
Vertical continuation in a system of equations
\begin{align} x_1 + y_1 &= 1 \\ x_2 + y_2 &= 2 \\ \vdots \\ x_n + y_n &= n \end{align}
Vertical continuation in a summation list
1 + 2 + 3 + \vdots + n