The
English language does not have definitive hyphenation rules, though various
style guides provide detailed usage recommendations and have a significant amount of overlap in what they advise. Hyphens are mostly used to break single words into parts or to join ordinarily separate words into single words. Spaces are not placed between a hyphen and either of the elements it connects except when using a suspended or "hanging" hyphen that stands in for a repeated word (e.g.,
nineteenth- and writers). Style conventions that apply to hyphens (and dashes) have evolved to support ease of reading in complex constructions; editors often accept deviations if they aid rather than hinder easy comprehension. The use of the hyphen in
English compound nouns and verbs has, in general, been steadily declining. Compounds that might once have been hyphenated are increasingly left with spaces or are combined into one word. Reflecting this changing usage, in 2007, the sixth edition of the
Shorter Oxford English Dictionary removed the hyphens from 16,000 entries, such as
fig-leaf (now
fig leaf),
pot-belly (now
pot belly), and
pigeon-hole (now
pigeonhole). The increasing prevalence of computer technology and the advent of the Internet have given rise to a subset of common nouns that might have been hyphenated in the past (e.g.,
toolbar,
hyperlink, and
pastebin). Despite decreased use, hyphenation remains the norm in certain compound-modifier constructions and, among some authors, with certain prefixes (see
below). Hyphenation is also routinely used as part of
syllabification in
justified texts to avoid unsightly spacing (especially in
columns with narrow
line lengths, as when used with
newspapers).
Separating Justification and line-wrapping When flowing text, it is sometimes preferable to break a word into two so that it continues on another line rather than moving the entire word to the next line. The word may be divided at the nearest break point between syllables (
syllabification) and a hyphen inserted to indicate that the letters form a word fragment, rather than a full word. This allows more efficient use of paper, allows flush appearance of right-side margins (
justification) without oddly large word spaces, and decreases the problem of
rivers. This kind of hyphenation is most useful when the width of the column (called the "line length" in typography) is very narrow. For example: Rules (or guidelines) for correct hyphenation vary between languages, and may be complex, and they can interact with other
orthographic and
typesetting practices.
Hyphenation algorithms, when employed in concert with dictionaries, are sufficient for all but the most formal texts. It may be necessary to distinguish an incidental line-break hyphen from one integral to a word
being mentioned (as when used in a
dictionary) or present in an original text being quoted (when in a
critical edition), not only to control its
word wrap behavior (which
encoding handles with
hard and soft hyphens having the same
glyph) but also to differentiate appearance (with a different glyph). ''
Webster's Third New International Dictionary and the Chambers Dictionary'' use a
double hyphen for integral hyphens and a single hyphen for line-breaks, whereas Kromhout's Afrikaans–English dictionary uses the opposite convention. The
Concise Oxford Dictionary (fifth edition) suggested repeating an integral hyphen at the start of the following line.
Prefixes and suffixes Prefixes (such as
de-,
pre-,
re-, and
non-) and
suffixes (such as '
, ', '
, and ') are sometimes hyphenated, especially when the unhyphenated spelling resembles another word or when the
affixation is deemed misinterpretable, ambiguous, or somehow "odd-looking" (for example, having two consecutive
monographs that look like the
digraphs of English, like e+a, e+e, or e+i). However, the unhyphenated style, which is also called
closed up or
solid, is usually preferred, particularly when the
derivative has been relatively familiarized or popularized through extensive use in various contexts. As a
rule of thumb, affixes are not hyphenated unless the lack of a hyphen would hurt clarity. The hyphen may be used between vowel letters (e.g.,
ee,
ea,
ei) to indicate that they do not form a
digraph. Some words have both hyphenated and unhyphenated variants:
/deescalate,
/cooperation,
/reexamine,
/deemphasize, and so on. Words often lose their hyphen as they become more common, such as
email instead of '
. When there are tripled letters, the hyphenated variant of these words is often more common (as in ' instead of ''''). Closed-up style is avoided in some cases: possible
homographs, such as
recreation (fun or sport) versus ''
(the act of creating again), retreat'' (turn back) versus '
(give therapy again), and ' (not in
ion form) versus
unionized (organized into
trade unions); combinations with
proper nouns or adjectives ('
, ');
acronyms ('
, '); or numbers ('
, '). Although ''
is still hyphenated by both Dorland's
and Merriam-Webster's Medical
, the solid (that is, unhyphenated) styling (protooncogene'') is a common variant, particularly among oncologists and geneticists. A
diaeresis may also be used in a like fashion, either to separate and mark off monographs (as in
coöperation) or to signalize a
vocalic terminal e (for example,
Brontë). This use of the diaeresis peaked in the late 19th and early 20th centuries, but it was never applied extensively across the language: only a handful of diaereses, including
coöperation and
Brontë, are encountered with any appreciable frequency in English; thus
reëxamine,
reïterate,
deëmphasize, etc. are seldom encountered. In borrowings from Modern French, whose
orthography utilizes the diaeresis as a means to differentiate
graphemes, various English dictionaries list the dieresis as optional (as in
naive and
naïve) despite the juxtaposition of a and i.
Syllabification and spelling Hyphens are occasionally used to denote
syllabification, as in
syl-la-bi-fi-ca-tion. Various British and North American dictionaries use an
interpunct (sometimes called a "middle dot" or "
hyphenation point"), for this purpose, as in
syl·la·bi·fi·ca·tion. This practice allows the hyphen to be reserved exclusively for instances where a true hyphen is intended for example,
self-con·scious,
un·self-con·scious, and
long-stand·ing.
Unicode provides a dedicated character for the hyphenation point, , "to be distinguished from [the interpunct], which has multiple semantics." Similarly, hyphens may be used to indicate the spelling of a word, as in
W-O-R-D to represent
word. In nineteenth-century American literature, hyphens were also used irregularly to divide syllables in words from indigenous North American languages, without regard for etymology or pronunciation, such as "Shuh-shuh-gah" (from
Ojibwe zhashagi, "blue heron") in
The Song of Hiawatha. This usage is now rare and deprecated, except in some place names such as
Ah-gwah-ching.
Joining Compound modifiers Compound modifiers are groups of two or more words that jointly modify the meaning of another word. When a compound modifier other than an
adverb–
adjective combination appears
before a term, the compound modifier is often hyphenated to prevent misunderstanding, such as in
player or
paintings. Without the hyphen, there is potential confusion about whether the writer means a "player of American football" or an "American player of football" and whether the writer means paintings that are "little celebrated" or "celebrated paintings" that are little. Compound modifiers can extend to three or more words, as in
candy, and can be adverbial as well as adjectival (
frightening). However, if the compound is a familiar one, it is usually unhyphenated. For example, some style guides prefer the construction
high school students, to
students. But permanent compounds, found as headwords in dictionaries, are treated as invariable, so if they are hyphenated in the cited dictionary, the hyphenation will be used in both attributive and predicative positions. For example, "A cost-effective method was used" and "The method was cost-effective" (
cost-effective is a permanent compound that is hyphenated as a headword in various dictionaries). When one of the parts of the modifier is a
proper noun or a
proper adjective, there is no hyphen (e.g., "a South American actor"). When the first modifier in a compound is an adverb ending in
-ly (e.g., "a poorly written novel"), various style guides advise no hyphen. In the 19th century, it was common to hyphenate adverb–adjective modifiers with the adverb ending in
-ly (e.g., "a craftily-constructed chair"). However, this has become rare. For example,
wholly owned subsidiary and
quickly moving vehicle are unambiguous, because the adverbs clearly modify the adjectives: "quickly" cannot modify "vehicle". However, if an adverb can also function as an adjective, then a hyphen may be or should be used for clarity, depending on the style guide. although not in predicative position (after the modified noun). This is applied whether numerals or words are used for the numbers. Thus
woman and
woman or
wingspan and
wingspan, but
the woman is 28 years old and
a wingspan of 32 feet. However, with symbols for
SI units (such as
m or
kg)—in contrast to the
names of these units (such as
metre or
kilogram)—the numerical value is always separated from it with a space:
a 25 kg sphere. When the unit names are spelled out, this recommendation does not apply:
a sphere,
a roll of film. In spelled-out
fractions, hyphens are usually used when the fraction is used as an adjective but not when it is used as a noun: thus
majority and
portion but
I drank two thirds of the bottle or
I kept three quarters of it for myself. However, at least one major style guide A commonly used alternative style is the hyphenated string (
hormone-receptor-positive cells,
cell-cycle-related factors). (For other aspects of en dash–versus–hyphen use, see
Dash § En dash.)
Object–verbal-noun compounds When an object is compounded with a verbal noun, such as
egg-beater (a tool that beats eggs), the result is sometimes hyphenated. Some authors do this consistently, others only for disambiguation; in this case,
egg-beater, egg beater, and
eggbeater are all common. An example of an ambiguous phrase appears in
they stood near a group of alien lovers, which without a hyphen implies that they stood near a group of lovers who were aliens;
they stood near a group of alien-lovers clarifies that they stood near a group of people who loved aliens, as "alien" can be either an adjective or a noun. On the other hand, in the phrase
a hungry pizza-lover, the hyphen will often be omitted (a hungry pizza lover), as "pizza" cannot be an adjective and the phrase is therefore unambiguous. Similarly,
a man-eating shark is nearly the opposite of
a man eating shark; the first refers to a shark that eats people, and the second to a man who eats
shark meat.
A government-monitoring program is a program that monitors the government, whereas
a government monitoring program is a government program that monitors something else.
Personal names Some married couples compose a new
surname (sometimes referred to as a
double-barrelled name) for their new family by combining their two surnames with a hyphen. Jane Doe and John Smith might become Jane and John Smith-Doe, or Doe-Smith, for instance. In some countries only the woman hyphenates her birth surname, appending her husband's surname. With already-hyphenated names, some parts are typically dropped. For example, Aaron Johnson and Samantha Taylor-Wood became
Aaron Taylor-Johnson and
Sam Taylor-Johnson. Not all hyphenated surnames are the result of marriage. For example
Julia Louis-Dreyfus is a descendant of Louis Lemlé Dreyfus whose son was Léopold Louis-Dreyfus. Hyphens are often used in romanization of
Korean names, such as
Ban Ki-moon and
Cho Jung-ho.
Other compounds Connecting hyphens are used in a large number of miscellaneous compounds, other than modifiers, such as in
lily-of-the-valley,
cock-a-hoop,
clever-clever,
tittle-tattle and
orang-utan. Use is often dictated by convention rather than fixed rules, and hyphenation styles may vary between authors; for example,
orang-utan is also written as
orangutan or
orang utan, and
lily-of-the-valley may be hyphenated or not.
Suspended hyphens A
suspended hyphen (also called a
suspensive hyphen or
hanging hyphen, or less commonly a
dangling or
floating hyphen) may be used when a single base word is used with separate, consecutive, hyphenated words that are connected by "and", "or", or "to". For example,
short-term and long-term plans may be written as
short- and long-term plans. This usage is now common and specifically recommended in some style guides. Suspended hyphens are also used, though less commonly, when the base word comes first, such as in "investor-owned and ". Uses such as "applied and sociolinguistics" (instead of "applied linguistics and sociolinguistics") are frowned upon; the Indiana University style guide uses this example and says "Do not 'take a shortcut' when the first expression is ordinarily open" (i.e., ordinarily two separate words). It is often used in
reduplication. Due to their similar appearances, hyphens are sometimes mistakenly used where an en dash or em dash would be more appropriate.
Varied meanings Some stark examples of semantic changes caused by the placement of hyphens to mark attributive phrases: •
Disease-causing poor nutrition is poor nutrition that causes disease. •
Disease causing poor nutrition is a disease that causes poor nutrition. • A
hard-working man is a man who works hard. • A
hard working man is a working man who is tough; however, this sense of
hard is rarely used before other adjectives. • A
man-eating shark is a shark that eats humans. • A
man eating shark is a man who is eating shark meat. •
Three-hundred-year-old trees are an indeterminate number of trees that are each 300 years old. •
Three hundred-year-old trees are three trees that are each 100 years old. •
Three hundred year-old trees are 300 trees that are each a year old. == Use in computing ==