Discussion Groups / English Usage / July 2009

In various guides to usage, e.g. IIRc Michael Swan, Modern English
Usage. At the askoxford.com website, which is run by the publishers of
the Oxford English Dictionary ther is among other things the foll9owing
guidance:

When is it correct to use a hyphen?

Hyphenation in English is highly variable, and in many contexts, it
really doesn't matter. The Fowler brothers, first editors of the Concise
Oxford Dictionary, wrote in their preface to the 1911 edition:

    We have also to admit that after trying hard at an early stage to
arrive at some principle that should teach us when to separate, when to
hyphen, and when to unite the parts of compound words, we had to abandon
the attempt as hopeless, and welter in the prevailing chaos.

The places where it does matter are summarized in the Oxford Pocket
Fowler's Modern English Usage (2004), the most important being

   1. to make clear the unifying of the sense in compound expressions
such as punch-drunk, cost-benefit analysis, or weight-carrying, or
compounds in attributive use (that is, in front of the noun), as in an
up-to-date list or the well-known performer;
   2. to join a prefix to a proper name (e.g. anti-Darwinian);
   3. to avoid misunderstanding by distinguishing phrases such as
twenty-odd people and twenty odd people, or a third-world conflict and a
third world conflict;
   4. to clarify the use of a prefix, as in recovering from an illness
and re-covering an umbrella;
   5. to clarify compounds with similar adjacent sounds, such as
sword-dance, co-opt, tool-like.
   6. to represent the use of a common element in a list of compounds,
such as four-, six-, and eight-legged animals.
   7. in dividing a word across a line-break. Guidance on word division
is given in reference books such as the Oxford Colour Spelling
Dictionary (1996).

I hope that helps, Einde O'Callaghan