“Continuous improvement” and “Continual improvement” are often used interchangeably and shouldn't be used in that manner. Continuous indicates duration without interruption. Continual indicates d uration that continues over a long period of time, but with intervals of interruption.
Continuous improvement means that organizations are in a constant state of driving process improvements. This involves a focus on linear and incremental improvement within existing processes. Continual improvements means that organizations go through process improvements in stages and these stages are separated by a period of time. This period of time might be necessary to understand if the improvements did actually help the bottom line. In some cases, the results might take a while to come to realization.
Continual and continuous improvement have nothing t o do with how the organization achieves the improvements but rather with whether the improvement is linear or not.