Is there a difference between "continual" and "continuous"?

They are very close in meaning, I know, but I want to know if there are any subtle differences. Let me give you an example of a subtle difference in meaning between synonyms:

Deceitful vs. deceptive

At first glance, these seem to be perfect synonyms. However, in putting them into sentences, one finds a pattern - deceitful is almost always used of persons, and deceptive is always used of situations or things. So the "perfect" synonyms cannot always replace each other.

My question is: is there a similar subtle difference between continuous and continual?

Solution 1:

Yes. Continuous means from some start to some end without break:

The water flowed continuously over the dam.

whereas continual means occurring repeatedly at intervals over a time span:

I continually lose at poker.

I should also mention that continual is often substituted for continuous, and would be correct in most contexts, however the converse is not generally true. That is to say,

The water flowed continually over the dam.

is okay, but you would (hopefully) not mean

I continuously lose at poker.

since that would imply that all you do all day long is play poker and lose.

Solution 2:

A compact discussion of continuous versus continual appears in wikipedia:

In English-language linguistic prescription, there is a common piece of usage advice that the word "continuous" should be used for things that are continuous in a way literally or figuratively equal to the mathematical sense of the word, whereas the word "continual" should be used for things that continue in discrete jumps (that is, quantum-wise). When this distinction is enforced, it is more accurate to speak of "continual improvement" and "continual improvement processes" than of "continuous improvement" or "continuous improvement processes".

The next paragraph of the article discusses a particular instance of mis-usage:

... for several decades it has been common usage in the linguistic corpus of business management to use the one set term, "continuous improvement", to cover both [forms] ... regardless of prescriptive preferences. However, ISO has chosen the more careful usage for its standards ... so it may be reasonable to expect that usage among business managers will evolve in coming decades to conform to the preferred usage...

Solution 3:

Based on Oxford dictionary, "continuous" can be used to refer to space as well as time, as in 'the development forms a continuous line along the coast'. "Continual", on the other hand, typically means ‘happening frequently, with intervals between’, as in 'the bus service has been disrupted by continual breakdowns'. Overall, continuous occurs much more frequently than continual (almost five times more often in the Oxford English Corpus).