Definition:Floor Function/Notation

Definition
Before around $1970$, the usual symbol for the floor function was $\left[{x}\right]$.

The notation $\left \lfloor {x} \right \rfloor$ for the floor function is a relatively recent development.

Compare the notation for the corresponding ceiling function, $\left\lceil{x}\right\rceil$, which in the context of discrete mathematics is used almost as much.