continual

Since the mid-19th century, many grammarians have drawn a distinction between continual and continuous. Continual should only mean "occurring at regular intervals," they insist, whereas continuous should be used to mean "continuing without interruption." This distinction overlooks the fact that continual is the older word and was used with both meanings for centuries before continuous appeared on the scene. The prescribed sense of continuous became established only in the 19th century, and it never succeeded in completely driving out the equivalent sense of continual. Today, continual is the more likely of the two to mean "recurring," but it also continues to be used, as it has been since the 14th century, with the meaning "continuing without interruption."