The hyphen ( ‐) is a punctuation mark used to join and to separate of a single word. The use of hyphens is called hyphenation. The hyphen should not be confused with (figure dash, en dash, em dash, ―), which are longer and have different uses, or with the minus sign (−), which is also longer in some contexts.
As an Orthography concept, the hyphen is a single entity. In terms of character encoding and display, that entity is represented by any of several characters and (including hard hyphens, soft or optional hyphens, and nonbreaking hyphens), depending on the context of use (discussed below).
Although hyphens are not to be confused with en dashes and minus signs, there are some overlaps in usage (in which either a hyphen or an en dash may be acceptable, depending on user preference; discussed below) and in character encoding (which often uses the same character, called a "hyphen-minus", to represent both the hyphen and minus sign entities; discussed below).
The term (ἡ) ὑφέν (( he) hyphén), was used for a tie-like (‿) sign written below two consecutive letters to indicate that they belong to the same word (when it was necessary to avoid ambiguity before the space was in regular use).
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", "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 measure, as when used with ).
|We, therefore, the|
representatives of the United
States of America...| style=width:3em;
|We, therefore, the |
tatives of the United States
The details of doing this properly are complex and language-dependent, and can interact with other Orthography and typesetting practices. Hyphenation algorithms, when employed in concert with dictionaries, are sufficient for all but the most formal texts. See also justification.
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). Merriam-Webster's Third New International Dictionary
Many long-established words, such as disgusted, degrade, and refresh, do not require a hyphen because they are fully fused to the point that their first syllable is barely even thought about as having a prefix function. Many other words, such as prewashed or repainted, may not be quite so fully fused (the prefix function may be slightly more prominent in consciousness), but nonetheless they require no hyphen, because (1) most readers recognize the closed-up word as a familiar one and thus have no trouble parsing the , and (2) if all such words were hyphenated, the many hyphens throughout the text would seem superfluous.
In contrast, for some other words, the closed-up style may not be as clear, and the hyphen can ensure clarity and avoid awkwardness, including "odd appearance" or misguided parsing of . An example of avoiding misguided parsing would be to hyphenate the word (versus coworker) to prevent the reader's eye being caught automatically by the letter group cow (which might suggest cattle () before backtracking and reparsing occurred). In such cases, styling varies depending on individual preference, regional preference, occupational specialty, or style guide preference, because the definition of "awkwardness" for any given word depends on who is judging it.
Words for which prefix hyphenation is least subjective, to the point that closed-up style is widely rejected, are of several classes. One such class consists of a few words that require a hyphen to distinguish them from other words that would otherwise be , 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 ). The other classes are those in which the prefix is applied to (1) a proper noun (capitalized) noun or adjective (, );.. (2) an acronym (, ); or (3) a number (, ).
Style guides codify rules to minimize inconsistency, the ultimate goal of which is to have the style unnoticed by the reader (that is, to avoid catching the reader's eye, either with trivial differences or with a lot of superfluous hyphens). The style guide rules allow exceptions to avoid awkwardness. For example, a guide will typically say to follow dictionary X's style for any word entered therein, and for words not entered, to close up by default and thus hyphenate only to avoid awkwardness. Such a rule successfully codifies almost all choices and thus leaves little to discretion except a few rare or neologistic words, which are safely hyphenated. This ensures high intradocument and interdocument consistency. Rules about avoiding doubled vowels or doubled consonants are often mentioned in style guides. These appropriately cascade only downstream, not upstream, of the "follow dictionary X" rule, because most dictionaries close up many well-established doubled-letter pairs. (For example, any style that follows Merriam-Webster's Collegiate Dictionary thus closes up preempt, reexamine, deemphasize, nonnegotiable, posttransfusion, and hundreds of others.) As mentioned earlier, the definition of "awkwardness" for any given word is inherently subjective but nonetheless also subject to consensus. For example, reexamine and deemphasize are accepted as nonawkward by a broad consensus; to prefer the hyphenated styling is a matter of opinion, but to insist that the solid styling is awkward would be considered pedantic by many educated readers. However, some doublings attract smaller majorities than others in such a consensus; with the / coworker example (mentioned earlier) or with antiinflammatory/, many readers may consider solid styling nonawkward whereas plenty of others don't, and in such cases, dictionary styles may vary ( Dorland's, antiinflammatory; Merriam-Webster's Medical Dictionary, ). Tripled letters rarely occur, but when they do, the hyphen is considered mandatory (thus , not shelllike).
There is a trend that over decades, words that once were hyphenated for clarity lose the hyphen as their familiarity grows. An excellent example is email/ ; the number of people who find email awkward dropped from the 1990s to the 2010s, and thus the hyphen has been dropped increasingly. For some instances, the consensus depends on occupational specialty or subspecialty. Although is still hyphenated by most users (and by both Dorland's and Merriam-Webster's Medical), the solid styling ( protooncogene) is gaining popularity, with oncologists and geneticists (for whom the term is most familiar) leading the way.
A hyphen can clarify that two adjacent —whether two of the same letter (e.g., oo, ee) or two different letters (e.g., ae, ei)—are pronounced separately rather than being merged in a diphthong. The question is how necessary the clarification is. Thus, hyphenated and have plenty of support, consensus-wise (plenty of users consider their hyphens as not superfluous), although solid deescalate and cooperation have plenty of support as well (plenty of users consider the hyphens superfluous). Consensus for styling varies by class, subclass, and even by individual word, with the common theme being that internal punctuation drops out of any combination judged as instantly recognizable enough in its context not to need it. As classes, there are doubling (namely, aa, ee, ii, oo, uu, yy) and nondoubling (for example, a+e, a+i, a+o; e+e, e+i, e+o). Several subclasses exist. There are combinations that are not rare in English as diphthongs and also not rare as nondiphthongs for users willing to style prefixed words solidly (such as ee and ei); regarding de+e/re+e/pre+e and de+i/re+i/pre+i, nearly everyone agrees that some fully fused examples (such as reiterate and reinforce) need no hyphen, but other examples have more evenly split pluralities (such as reexamine/ or deemphasize/). There are combinations that are rare in English as diphthongs (for example, aa and ii) but not rare in prefixed words for those willing to style them solidly; and thus either they hardly need clarification within prefixed words (the solidification argument; thus intraarterial and antiinflammatory) or they need a hyphen to avoid looking like rare diphthongs, which are "odd-looking" because rare (the hyphenation argument, thus and ).
A diaeresis can also sometimes be used, either to indicate nondiphthong status (e.g., coöperation and naïve) or to indicate non-silent terminal -e (e.g., Brontë), but there are several implicit boundaries on this style's use; it is now rare (its peak of popularity was in the late 19th and early 20th centuries), and it was never applied extensively across the language (only a handful of examples, including coöperation, naïve, and Brontë, are encountered with any appreciable frequency in English; for whatever reason, it never had any popularity in the de+e/re+e/pre+e or de+i/re+i/pre+i subclasses—thus never *reëxamine, *reïterate, *deëmphasize, or others, although they might have been useful). Many users (and various dictionaries) consider the diaeresis optional in naive/ naïve (because not necessary for the reader to recognize the word), and *na-ive draws attention to itself as a style that is simply never used (although comprehensible). For deity and deify, only solid styling (no hyphen or diaeresis) is normative.
When a compound modifier follows the term to which it applies, a hyphen is typically not used if the compound is a temporary compound. For example, "that gentleman is well respected", not "that gentleman is well-respected"; or "a patient-centered approach was used" but "the approach was patient centered." 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. However, some do allow for this use. For example, The Economist Style Guide advises: "Adverbs do not need to be linked to participles or adjectives by hyphens in simple constructions .... Less common adverbs, including all those that end -ly, are less likely to need hyphens". 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. For example, the phrase reasons ("reasons that are more important") is distinguished from more important reasons ("additional important reasons"), where more is an adjective. Similarly, scenery (with a mass noun) is distinct from more beautiful scenery. (In contrast, the hyphen in "a reason" is not necessary, because the syntax cannot be misinterpreted.) A few short and common words – such as well, ill, little, and much – attract special attention in this category. The hyphen in "well-past_participled noun", such as in "well-differentiated cells", might reasonably be judged superfluous (the syntax is unlikely to be misinterpreted), yet plenty of style guides call for it. Because early has both adverbial and adjectival senses, its hyphenation can attract attention; some editors, due to comparison with advanced-stage disease and adult-onset disease, like the parallelism of early-stage disease and early-onset disease. Similarly, the hyphen in little-celebrated paintings clarifies that one is not speaking of little paintings.
Hyphens are usually used to connect numbers and words in modifying phrases. Such is the case when used to describe dimensional measurements of weight, size, and time, under the rationale that, like other compound modifiers, they take hyphens in attributive position (before the modified noun),
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 hyphenates spelled-out fractions invariably (whether adjective or noun).
In English, an en dash ( – ) sometimes replaces the hyphen in hyphenated compounds if either of its constituent parts is already hyphenated or contains a space (for example, San Francisco–area residents, hormone receptor–positive cells, cell cycle–related factors, and public-school–private-school rivalries).
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, there's a man-eating shark in these waters is nearly the opposite of there's a man eating shark at table 6; the first is a shark, and the second a man. A government-monitoring program is a program that monitors the government, whereas a government monitoring program is a government program that monitors something else.
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.
The hyphen is sometimes used to hide letters in words (filleting for redaction/censoring), as in G-d, although an en dash can be used as well ("G–d").
The hyphen is often used in Reduplication.
With the introduction of letter-spacing in the Middle Ages, the hyphen, still written beneath the text, reversed its meaning. Scribes used the mark to connect two words that had been incorrectly separated by a space. This era also saw the introduction of the marginal hyphen, for words broken across lines.
The modern format of the hyphen originated with Johannes Gutenberg of Mainz, Germany, with the publication of his 42-line Gutenberg Bible. His tools did not allow for a subliminal hyphen, and he thus moved it to the middle of the line.
However, the Unicode hyphen is awkward to enter on most keyboards, so the hyphen-minus character remains very common. They are often used instead of dashes or minus signs in situations where the preferred characters are unavailable (such as ASCII-only text), where the preferred characters take effort to enter (via or multi-key, unmemorable keyboard shortcuts), or when the writer is unaware of the distinction. Some writers use two hyphen-minuses (--) to represent a dash in ASCII text.
The ASCII hyphen-minus character is also often used when specifying command-line options. The character is usually followed by one or more letters that indicate specific actions. Typically it is called a dash or switch in this context. Various implementations of the getopt function to parse command-line options additionally allow the use of two hyphen-minus characters ( -- ) to specify long option names that are more descriptive than their single-letter equivalents. Another use of hyphens is that employed by programs written with pipelining in mind: a single hyphen may be recognized of a filename, with the hyphen then serving as an indicator that a standard streams, instead of a file, is to be worked with.
In contrast, a hyphen that is always displayed and printed is called a hard hyphen (although some use this term to refer to a non-breaking hyphen; see below). Soft hyphens are inserted into the text at the positions where hyphenation may occur. It can be a tedious task to insert the soft hyphens by hand, and tools using hyphenation algorithms are available that do this automatically. Current modules of the Cascading Style Sheets (CSS) standard provide language-specific hyphenation dictionaries.
The word segmentation rules of most text systems consider a hyphen to be a word boundary and a valid point at which to break a line when flowing text. However, this is not always desirable behavior, especially when it could lead to ambiguity (such as in the examples given before, where recreation and re‑creation would be indistinguishable), or in languages other than English (e.g., a line break at the hyphen in Irish language an t‑athair or Romanian s‑a would be undesirable). In Unicode it is defined as .
International standard ISO 8601, which was accepted as European Standard EN 28601 and incorporated into various typographic style guides (e.g., DIN 5008 in Germany), brought about a new standard using the hyphen. Now all official European governmental documents use this. These norms prescribe writing dates using hyphens: 1789-07-14 is the new way of writing the first Bastille Day. This is also the typical date format used in large parts of Eastern Europe and Asia, although sometimes with other separators than the hyphen.
This method has gained influence within North America, as most common computer filesystems make the use of slashes difficult or impossible. DOS, OS/2 and Windows simultaneously support both \ and / as directory separators, but / is also used to introduce and separate switches to shell commands (unless reconfigured to use the hyphen-minus in DOS). Unix-like systems use / as a directory separator and, while \ is legal in filenames, it is awkward to use as the shell uses it as an escape character. Unix also uses a space followed by a hyphen to introduce switches. Apart from the separator used the non-year form of the date format is also identical to the standard American representation.
(See interpunct for more round characters.)