Iverson bracket

Etymology
Named after, who introduced this notation in his programming language APL.

Noun

 * 1)  A notation that denotes a number that is 1 if the condition in square brackets is satisfied, and 0 otherwise, i.e. (where P is a true or false statement)
 * $$[P] = \begin{cases} 1 & \text{if } P \text{ is true;} \\ 0 & \text{otherwise.} \end{cases}$$