"...measurement procedure for obtaining a tally or count of the number of times a behavior occurs" (Cooper et al, 2007, p. 695).

Refers to the fact that a behavior can occur repeatedly through time (i.e., behavior can be counted) (e.g., count, frequency, rate)

Refers to the fact that every instance of behavior occurs during some amount of time

Behavior occurs at a certain point in time with respect to other events

Dividing behavior into time intervals and noting whether the behavior did/did not occur during (or at end) of interval