continual

continual, continuous

1. Continual is the older word (14c), and once had all the meanings it now (since the mid-19c) shares with continuous (17c). Fowler (1926) expressed the current distinction somewhat cryptically as follows: ‘That is -al which either is always going on or occurs at short intervals and never comes (or is regarded as never coming) to an end. That is -ous in which no break occurs between the beginning and the (not necessarily or even presumably long-deferred) end.’

2. Continuous is used in physical contexts (such as lines, roads, etc.) and is preferred in technical contexts (e.g. continuous assessment / continuous playback / continuous stationery). The other principal use is with reference to time: continuous here means ‘going on uninterrupted’ whereas continual means ‘constantly or frequently recurring’. The following examples show how difficult it is to keep the two meanings apart:

• The correspondence between the two men was continuous throughout the next few months —V. Brome, 1978

• The 1840s were years of continuous self-education for Philip Henry Gosse —A. Thwaite, 1984

• The house and garden had seen their best days, and the decline was now continual, from season to season —R. Frame, 1986

• His son was a continual source of amusement and delight to him —E. Blair, 1990

• He singled out two big issues that should be addressed: ‘The first is the continual underfunding of road and rail infrastructure.’ —Lloyd's List, 2006.

Note that other words are sometimes preferable, e.g. (in place of continual) constant, habitual, intermittent, recurrent, repeated, and (in place of continuous) ceaseless, constant, incessant, unbroken, uninterrupted. Note also that constant can be used to mean both continual and continuous.

3. Of the corresponding adverbs, continually (14c) is older by far than continuously (17c). Here, for some reason, the current distinction is clearer to see; continually can be defined as ‘repeatedly; again and again’ and continuously as ‘without interruption’:

• This lost energy must be continuously supplied by the engines —C. E. Dole, 1971

• He said that the business of the court…was being continually held up by irrelevancies —J. B. Morton, 1974

• The black coat had lost its warmth and he shivered continually —J. M. Coetzee, 1983

• Clinical governance requires that the quality of medical care be continuously monitored —Bath Chronicle, 2001.

In the following example, continuously seems to be wrongly used for continually:

• The Chinese officials also continuously stated that they could put a stop to inflation at any time —P. Lowe, 1989.