In ITIL, you have probably heard of Continual Service Improvement, and in DevOps, there are processes such as Continuous Integration and Continuous Delivery. If you notice closely, the word that I am using with ITIL is continual and the one with DevOps is continuous. Are these words the same? Can they be interchanged? Well, the answer is no, and no!
Continuous = without interruption [Oxford Dictionary]
Continuous refers to something that happens over a period of time without interruptions. An example that is popularly used, is an incline plane. The incline plane continues to take off in an upward direction without any disruptions or inhibitions in between.
Continual = Forming a sequence in which the same action or event is repeated frequently [Oxford Dictionary]
Whereas continual is just the opposite, by design. When an event happens at regular frequencies, it is referred to as continual. In the same example of an incline plane, the plane moves upward until there are occurrences of flat periods. These flat periods occur at regular frequencies.
Service improvements in ITIL are continual in nature and not continuous use after every single improvement, a period of stabilization is desired. Unless stabilization is achieved, the services offered will suffer from various SLA breaches that could result from improvements not gone right.
Continuous Integration and Continuous Delivery in DevOps is meant to be uninterrupted, to ensure speedy delivery of software. In DevOps, wasting resources, and wasting time is unwanted, and therefore, the processes are meant to be continuous, without any glitches and hitches.
So, as you can discern, the words continuous and continual cannot be interchanged. Each of these words has a specific meaning and a specific purpose.