The French spelling reform: use of the hyphen
The French spelling reform proposes minor changes to the use of hyphens.
Use of hyphens in numbers
Prior to the reform, no hyphen was used around the word et or words such as cent(s), mille etc when writing compound numbers. The reform proposes that the hyphen is placed between all words of a compound number:
In our survey, 54% of respondents preferred the form vingt-et-un over the older form vingt et un.
Loss of hyphens in foreign and compound words
In current conventional usage, the hyphen is used in certain compounds where each part of the compound carries its individual sense. So for example, a porte-hélicoptère actually carries a helicopter; a chauffe-eau actually heats water.
In other cases, the hyphen is used in words where the two elements no longer have any individual sense in French or are not perceived as individual units, or in loanwords. For example, the word chausse-trappe (a "trap" used to hunt animals) derives from an older meaning of the word chausser which used to mean "to trip up", but now is only used in the meaning of "to put shoes on". In the loanword week-end, conventionally still written with a hyphen in French even though this is now rare in English, there is little sense of week and end being individual words of French.
There are also various "onomatopoeic" words such as kif-kif, pique-nique, prêchi-prêcha etc.
In general, where there isn't a strong sense of each element of the compound carrying its individual meaning in modern French, it is proposed that the hyphen be done away with.
In fact, this has already happened historically in a few cases: a porte-feuille in the sixteenth century denoted an item for carrying documents (feuilles or "leaves" of paper)1; nowadays, it tends to denote a "wallet" for carrying money, and tends to be written without a hyphen (portefeuille).
The original reform proposal includes several short lists of words that are affected by this rule. These include words whose meaning isn't guessable from the elements, such as chausse(-)trappe and tire(-)fond (actually a type of screw or bolt). But it also includes various words whose meaning is clearer, such as porte(-)clé and tire(-)bouchon. These are presumably chosen because, as the document later phrases it in its recommendations to lexicographers on the use of hyphens, they are "felt to be a single lexical unit".
Perhaps unsurprisingly, there appears to be a little discrepancy between the words listed in the original proposal and those marked by dictionaries as being affected by the proposed change. Larousse, for example, list porte-plume as being a candidate for re-spelling as porteplume, but this word is not one of the ones listed in the original proposal. The latter does indicate that it expects the rule to apply generally: "Il était exclu de modifier d'un coup plusieurs milliers de mots composés, l'usage pourra le faire progressivement". But it doesn't explicitly state how far it expects this rule to go, and whether it expects dictionaries to one day advocate the form portehélicoptère.
Some of the "new" forms listed (such as tapecul) already alternate with their hyphenated counterparts in current usage.
It is also proposed that the hyphen be avoided with scientific prefixes, so that whereas current usage fluctuates between agro-alimentaire and agroalimentaire, the latter is advocated in the reform. Similarly, one would write ultrafiltration instead of ultra-filtration, infra-rouge and not infrarouge etc.
1. cf Larousse, "Dictionnaire du moyen français"