# Column or row of a matrix?

The question is so simple, but I cannot find the answer.

Is $M_i$ (usually) the $i^{\text{th}}$ column of matrix $M$? Or the $i^{\text{th}}$ row?

Since $M_{ij}$ is the $j^{\text{th}}$ element of the $i^{\text{th}}$ row, I would say $M_i$ is the row.
On the other hand we usually work with column vectors and it is therefore unusual to take a row from a matrix and it would be illogical to have a simple notation for something that is used less often.

If $M_i$ is the $i^{\text{th}}$ row, how would I get the $i^{\text{th}}$ column? Surely not $(M^T)_i$!