User:Tony1/Hyphens and dashes
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[edit] Hyphens
Hyphens (-) indicate conjunction. There are three main uses.
- To distinguish between homographs (“re-dress” = dress again, but “redress” = remedy or set right).
- To link certain prefixes with their main word (“non-linear”, “sub-section”, “super-achiever”). However, a clear tendency is emerging to join both elements in all varieties of English (“subsection” is now standard), particularly in North America (where “nonlinear” is also standard).
- The hyphen is more likely to be used when the letters brought into contact are vowels, especially the same vowel (“co-opt”, “pre-existing”), or where a word is unusual, or less expected in the context (“co-owned”, “re-anchor”).
- It is common not to hyphenate simple and recognizable cases (“coopt”, “preexisting”; but certainly not “coowned”, and probably not “reanchor”).
- The hyphen is always used to avoid doubling “a” or “i”: “intra-atomic”, “juxta-articular”, “semi-intensive”.
- The hyphen is sometimes retained after “sub-” to avoid bringing two consonants into contact, and always to avoid doubling “b” (“subabdominal”, but “sub-basement”). It is also often retained for clarity when the main word begins with a vowel, or is short—especially when both of these apply (“sub-era”, not “subera”).
- The hyphen is still often used after “non-”, and always when “n” would be doubled (“non-linear” or “nonlinear”, as above; but “non-negotiable”).
- To link related terms in compound adjectives.
- Sometimes the hyphen helps with ease of reading (“face-to-face discussion”, “18th-century music”); hyphens are particularly useful in long nominal groups where non-experts are part of the readership, such as in Wikipedia's scientific articles: “gas-phase reaction dynamics”.
- Sometimes the hyphen helps with disambiguation (“little-used car”, not a reference to the size of a used car).
- Many compound adjectives that are hyphenated when used attributively (before the noun they qualify—“a light-blue handbag”), are not hyphenated when used predicatively (after the noun—“the handbag was light blue”). Where there would be a loss of clarity, the hyphen may be used (“hand-fed turkeys”, “the turkeys were hand-fed”).
- Hyphens are not used after “-ly” adverbs (“wholly owned subsidiary”), with the rare exception of larger compounds (“a slowly-but-surely strategy”).
- A hyphen is normally used when the adverb “well” precedes a participle used attributively (“a well-meaning gesture”); and even predicatively, if “well” is necessary to, or alters, the sense of the adjective (“the gesture was well-meaning”, “the child was well-behaved”, but “the floor was well polished”).
- A hanging hyphen is used when two compound adjectives are separated (“two- and three-digit numbers”; or less commonly “Hire a ten-car or -truck convoy, whichever is more suitable”).
- Values and units used as compound adjectives are hyphenated only where the unit is fully spelled out. Where hyphens are not used, values and units are always separated by a non-breaking space ( ).
- ✔ 9-mm gap
- ✔ 9 mm gap (rendered as 9 mm gap)
- ✖ 9 millimetre gap
- ✔ 9-millimetre gap
- ✔ nine-millimetre gap
- ✔ 12-hour shift
- ✔ 12 h shift
Hyphens are never followed or preceded by a space, except when hanging or when used to display parts of words independently, such as the prefix “sub-” and the suffix “-less”. Hyphens are used only to mark conjunctions; on Wikipedia, they have often been wrongly used to mark disjunction (for which en dashes are correct: see below).
[edit] En dashes
En dashes (–) have four distinct roles.
- To indicate disjunction. In this role there are two main applications.
- To convey to, particularly in ranges (“pp. 211–19”, “64–75%”, “the 1939–45 war”, “May–November”) and where movement is involved (“Dublin–Belfast route”). Year and page ranges are often an issue on Wikipedia. The word to is used instead of an en dash when a number range involves a negative value or might be misconstrued as subtraction (“−3 to −1”). In any case, to is used instead of an en dash when the nearby wording demands it (“from p. 195 to p. 250”, not “from pp. 195–250”).
- As a substitute for some uses of “and”, for marking a relationship involving independent elements in certain compound expressions (“Canada–US border”, “blood–brain barrier”, “time–altitude graph”, “4–3 win in the opening game”, “male–female ratio”, “3–2 majority verdict”; but a hyphen is used instead in “Mon-Khmer languages” which lacks a relationship, “Sino-Japanese trade”, in which “Sino-” lacks independence, and “Indo-European linguistics” which lacks both relationship and lexical independence).
- To represent minus signs (“–8 ºC”), always unspaced, and operators (“42 – 4 = 38”), always spaced. In these roles, the slightly shorter hyphen-minus signs (−) may be used instead; many scientists consider it to be mandatory for minus signs and operators.
- In lists, to separate distinct information within points—particularly track titles and durations, and musicians and their instruments, in articles on music albums. In this role, en dashes are always spaced.
- As a stylistic alternative to em dashes (see below).
Hyphens have often been wrongly used in disjunctive expressions on Wikipedia; this is especially common in sports scores. When creating an article, a hyphen is now not used as a substitute for an en dash in the title.
The main article shows common input methods for en dashes on Macintosh and Windows.
[edit] Em dashes
Em dashes (—) indicate interruption. They can be used in the following two roles.
- Parenthesis (“Wikipedia—one of the most popular web sites—has the information you need”). Here, a pair of em dashes is a more arresting way of nesting a phrase or clause than a pair of commas, and may be less intrusive than brackets. A pair of em dashes is particularly useful where there are already many commas; em dashes can make a sentence with more than one nesting easier to read, and sometimes they can remove ambiguity.
- A sharp break in the flow of a sentence—sharper than is provided by a colon or a semicolon.
Em dashes are unspaced on Wikipedia.
Because em dashes are visually striking, Wikipedia takes care not to overuse them. A rule of thumb is to avoid more than two in a single paragraph, unless the paragraph is unusually long or the use of more than two em dashes would be logically cohesive. Only very rarely are there more than two em dashes in a single sentence.
The main article shows common input methods for em dashes on Macintosh and Windows.
[edit] Spaced en dashes as an alternative to em dashes
Spaced en dashes ( – ) can be used instead of em dashes in all of the ways discussed above. Spaced en dashes – such as here – are used by several major publishers, to the complete exclusion of em dashes. Style manuals more often prefer unspaced em dashes. One style should be used consistently in an article.
- Other dashes
These are avoided on Wikipedia, notably the double-hyphen (--).
