Q: I am curious about the words “continual” and “continuous.” Is there a difference between them and when should each one be used?
A: Many usage guides make this distinction: “continual” means going on regularly or frequently but with breaks in between; “continuous” means going on steadily and without interruption. Bryan A. Garner, in Garner’s Modern American Usage, offers a trick for telling them apart—imagine that the “ous” ending is short for “one uninterrupted sequence.”
These days, however, so many people use the two words interchangeably that the distinction may someday be lost. In fact, a case can be made that the difference between “continual” and “continuous” has never been quite as clear-cut as the sticklers insist.
The word “continual,” for instance, has been used to mean both continuing without interruption and repeated with brief interruptions since the 14th century, according to the Oxford English Dictionary. The 17th-century newcomer “continuous,” the OED says, means uninterrupted or unbroken.
Both The American Heritage Dictionary of the English Language (4th ed.) and Merriam-Webster’s Collegiate Dictionary (11th ed.) define “continuous” as uninterrupted, but they say “continual” can mean either uninterrupted or recurring regularly.
Because people use both to imply without interruption, it’s better to use “repeated” or “intermittent” instead of “continual” to describe something that starts and stops.