单数they是they或它的词形变化形式（例如them或their）的用法，用于指单独一个人，作为单数形式。
典型地，这种情况出现于不确定的性别，例句：
类似地，这种情况也可以应用于派生词，例如themself或themselves。
这种用法的一个原因是英语没有专用于不确定性别的单数人称代词。有些情况，这种用法可以被解释为一种名义约定，因为如everyone之类的单词，虽然在语法上是单数形式，但事实上却是复数的意义。这种用法逐渐变多的一个原因可能是20世纪的性别包容语言运动，但是它已经被有影响力的作家使用了好几个世纪。
虽然单数they的用法历史悠久，并且在日常英语中广泛使用，但是这种用法从19世纪末开始还是一直受到批评，并且大家的认可度也不同。
单数they与“正常”的复数they有相同的词形变化形式，即them和their。它们通常都使用相同的动词形式，也就是说“when I tell someone a joke laughs”是不规范的。
反身代词themselves有时也被使用，但是还有一个可选的反身代词形式themself。虽然themself有历史悠久并且在20世纪80年代复活了，但是它还是依然较少使用，并且只被少数人认可。 它在指代性别不明的单个人的时候有时使用，因为这时候复数形式themselves看起来不协调，例如
单数themself在加拿大联邦法律文本中被系统化地使用，用于区别于复数themselves。
早在14世纪的中古英语，they就一直被用于单数形式。 在许多知名作家的著作中都能看来这种用法，包括杰弗里·乔叟、威廉·莎士比亚、简·奥斯丁、威廉·梅克比斯·萨克雷和萧伯纳：
同时，除了使用they，使用代词he作为（据称的）性别中性代词也被认可，如下所述：
在威廉·梅克比斯·萨克雷的著作中，两个都出现过：
与
并且威廉·卡克斯顿写道：
alongside
在非正式英语中使用he而非they的用法的倡导，可以在18世纪中叶找到，在Ann Fisher（英语：Ann Fisher）的《A New Grammar》中写道：
性别通用名使用阳性，可以理解为男性与女性，正如 (引自Ostade)
1895年的语法（Baskervill, W.M.与Sewell, J.W.的《An English Grammar for the Use of High School, Academy and College Class》）标记了单数they的通用的用法，但是推荐用性别通用he，基于数协议：
指代前面出现过的泛指代词或者被泛指形容词修饰的名词的另一种方法，是在后面使用复数代词。这并不是最好的用法，逻辑上显然需要使用单数代词，但是这种结构经常出现于。阳性词并不能表示阴性，并且应该避免 his or her 的表示法，因为很笨重.
Baskervill给出了知名作家的使用单数they的一些例子，包括
但是他更喜欢使用he：
当前面说的包括男性与女性的时候，或者是一个泛指性的单词的时候，最好的方法是后续代词使用阳性单数代词
—Baskervill, An English Grammar
1850年，英国议会通过了一个法案，其中说了，在议会的法案中使用的时候“阳性词必须被视为包括女性”。
据称的性别中性的he的用法直到至少20世纪60年代还能用，虽然有一些he的用法后来因笨拙或愚蠢而被批评，例如指代：
当代著作在指代性别通用或不确定的前面出现的词的时候，有时还是可以看到使用he。有时指代的人几乎可以确定为男的，例如
有时前面出现的词指代的人只是男的或者这种职业传统上只有男性人员：
还有其它情况，前面的词可能指代：
甚至在2010年，还是可以发现性别通用he的建议：
在20世纪的下半个世纪，女权主义者关注“性别歧视主义”的男性导向式语言。不但包括man性别通用，而且包括he作为性别通用代词。
争论点是he不能明智地作为性别通用代词，包括男人与女人。William Safire在他的《纽约时报》的 On Language 专栏上赞同了性别通用he，提及口诀“男性包罗女性”。Brooklyn的C. Adendyck对《纽约时报》写了一个回复：
"The average American needs the small routines of getting ready for work. As he shaves or blow-dries his hair or pulls on his panty-hose, he is easing himself by small stages into the demands of the day."
1980年，运动受到广泛支持，许多组织，包括绝大多数出版社，都发行了性别中性语言的使用指南。
在一些情况，可能知道个体但却用they来指代，因为性别未知或者因为他/她偏爱使用they，例如社会媒体应用，可能允许账号持有者来选择非常规性别例如性别酷儿或双性别和一个代词，包括他们可能愿意使用的they/them。
自从20世纪60年代以来，在书面语和口语中使用阳性通用名词和代词的频率就在一减少。20世纪90年代在澳大利亚收集的自发讲话语料库中，单数变最频繁使用的通用代词。单数的使用上升的原因，至少是部分原因，是性别中性语言的使用的增长。一百年前的作者用作为不确定性别的指代时可能没有顾虑，但是如今的作者经常会感觉这么用不自在。在正式场合的一种方案通常是写或者其它类似的，但是过度使用这种方式感觉很别扭，或者感觉很政治正确，或者都有。
当代用法中，单数常被用于指定性别不确定的先行词，至少有一些人这么用，例如当先行词的性别或数量不确定、未知或未揭露的时候。例子包括不同类型的用法。
单数先行词可以是一个代词，例如everybody、someone、anybody或者疑问代词例如who：
单数先行词也可以是一个名词，例如（个人）、（病人）或（学生）：
有些人比其他人有更大的被接受度，在某些情况下尝试用（形态上）单数代词来替换会得到荒唐的结果，可以用上面的例子验证。
虽然性别通用和性别通用作为单数代词使用有很长的一段历史了，并且它们至今都依然还在使用中，但是它们还是一直被部分人群系统化地避免使用。防止表述偏袒任何一方的风格指引有时建议把这些通用的表达重新表述为复数形式来避免被任何一方指责。
单数的使用在英国英语中比在美国英语中更加被广泛接受 or vice versa.
一性用法指引我们接受被建议的单数用法并不是仅仅是用于语义复数的单数词例如everyone，而且也用于前面指代的不确定的“个人”，这些用法的例子甚至常出现在正式演讲中。例如，Casey Miller和Kate Swift，在《无性别歧视写作手册》（The Handbook of Non-Sexist Writing）， Ronald Reagan引用：
(2003)推荐小心使用单数，并且尽可能避免使用，因为这么用有点别扭。
Garner认为单数的使用在英国英语中的接受度更大一些：
并且美国英语使用者显然抵制这种变化:
他将使用单数they和everyone，anyone和somebody等先行词的趋势视为不可避免的:
In the 14th edition (1993) of , the University of Chicago Press explicitly recommended use of singular use of and , noting a "revival" of this usage and citing "its venerable use by such writers as Addison, Austen, Chesterfield, Fielding, Ruskin, Scott, and Shakespeare."From the 15th edition, this was changed. In Chapter 5 of the 16th edition, now written by Bryan A. Garner, the recommendations are:
and
According to , many Americans avoid use of to refer to a singular antecedent out of respect for a "traditional" grammatical rule, despite use of singular by modern writers of note and mainstream publications:
The explicitly reject the use of singular and gives the following example as "incorrect" usage:
while also specifically taking a stand that generic is unacceptable. The APA recommends using , recasting the sentence with a plural subject to allow correct use of , or simply rewriting the sentence to avoid issues with gender or number.
Strunk & White, the authors of find use of with a singular antecedent unacceptable:
Their assessment, in 1979, was
Joseph M. Williams, who wrote a number of books on writing with "clarity and grace", discusses the advantages and disadvantages of various solutions when faced with the problem of referring to an antecedent such as , , or a noun that does not indicate gender and suggests that this will continue to be a problem for some time. He "suspect that eventually we will accept the plural as a correct singular" but states that currently "formal usage requires a singular pronoun".
According to , most experts—and some teachers and employers—find use of singular unacceptable:
It recommends using or avoiding the problem by rewriting the sentence to use a plural or omit the pronoun.
The (OWL) maintains that singular is incorrect:
In the first edition of (published in 1926) it is stated that singular is disapproved of by grammarians and should be avoided in favour of the generic . Examples of its use by eminent writers are given, but it is suggested that "few good modern writers would flout so conspicuously as Fielding and Thackeray", whose sentences are described as having an "old-fashioned sound".
In the second edition of Fowler's, (edited by Sir Ernest Gowers and published in 1965), it is stated that singular is disapproved of by grammarians and, while common in colloquial speech, should preferably be avoided in favour of the generic in prose. Numerous examples of its use by eminent writers are given, but it is still suggested that "few good modern writers would flout so conspicuously as Fielding and Thackeray".
According to the third edition of Fowler's (, edited by Burchfield and published in 1996) singular has not only been widely used by good writers for centuries, but is now generally accepted, except by some conservative grammarians, including the Fowler of 1926, who ignored the evidence:
was originally written in 1948 by Sir Ernest Gowers, a civil servant, in an attempt by the British civil service to improve "official English". A second edition, edited by Sir Bruce Fraser, was published in 1973. It refers to or as the "equivalent of a singular pronoun of common sex" as "common in speech and not unknown in serious writing " but "stigmatized by grammarians as usage grammatically indefensible. The books advice for "official writers" (civil servants) is to avoid its use and not to be tempted by its "greater convenience", though "necessity may eventually force it into the category of accepted idiom".
A new edition of , revised and updated by Sir Ernest Gowers' great granddaughter, Rebecca Gowers, was published in 2014.It notes that singular and have become much more widespread since Gowers' original comments, but still finds it "safer" to treat a sentence like 'The reader may toss their book aside' as incorrect "in formal English", while rejecting even more strongly sentences like
(first published in 2003 by of London) recommends avoiding sentences like
by using a plural construction:
they
It expresses several preferences.
refers to the use of in sentences like
as "scrambled syntax that people adopt because they cannot bring themselves to use a singular pronoun".
is aimed at those engaged in copy editing, and the emphasis is on the formal elements of presentation including punctuation and typeface, rather than on linguistic style but—like —makes occasional forays into matters of usage.It advises against use of the purportedly gender-neutral , and suggests cautious use of where presents problems.
The 2011 edition of the uses singular y instead of the traditional when translating pronouns that apply to both genders in the original Greek or Hebrew. This decision was based on research by a commission that studied modern English usage and determined that singular (/) was by far the most common way that English-language speakers and writers today refer back to singular antecedents such as , , , , , and the like."
The Australian recommends "Gender-neutral language should be used", stating that use of and as singular pronouns is acceptable.
According to (1985):
discusses the prescriptivist argument that is a plural pronoun and that the use of with a singular "antecedent" therefore violates the rule of agreement between antecedent and pronoun, but takes the view that , though plural, can also be singular in a secondary sense, comparable to the purportedly extended sense of to include female gender.
Use of singular is stated to be "particularly common", even "stylistically neutral" with antecedents such as , , and , but more restricted when referring to common nouns as antecedents, as in
Use of the pronoun is described as being "rare" and "acceptable only to a minority of speakers", while use of the morphologically plural is considered problematic when referring to rather that (since only the latter implies a plural set).
There are also issues of grammatical acceptability when reflexive pronouns refer to singular noun phrases joined by , the following all being problematic:
On the motivation for using singular , states
The alternative can be "far too cumbersome", as in
or even " flatly ungrammatical", as in
"Among younger speakers", use of singular even with definite noun-phrase antecedents finds increasing acceptance, "sidestepping any presumption about the sex of the person referred to", as in
Steven Pinker suggests that "singular" and plural can be regarded as a pair of homonyms — two words with different meanings but the same spelling and sound. However, this analysis is not extended to , another originally plural pronoun that has come to have singular use.
Distributive constructions apply a idea to members of a group.They are typically marked in English by words like , and . The simplest examples are applied to groups of two, and use words like and —"Would you like tea or coffee?". Since distributive constructions apply an idea relevant to each individual in the group, rather than to the group as a whole, they are most often conceived of as singular, and a singular pronoun is used.
However, many languages, including English, show ambivalence in this regard. Because distribution also requires a group with more than one member, plural forms are sometimes used.
According to the traditional analysis, English personal pronouns (e.g. , , ) are typically used to refer backward (or forward) within a sentence to a noun phrase (which may be a simple noun). This reference is called an reference, and the referring pronoun is termed an .
The so-called singular is morphologically plural, and is accompanied by a plural verb. However, it is often used in circumstances where an indeterminate antecedent is signified by an indefinite singular antecedent; for example,
In some sentences, typically those including words like or , the morphologically singular antecedent does not refer to a single entity but is "anaphorically linked" to the associated pronoun to indicate a set of pairwise relationships, as in the sentence:
One explanation given for the use of to refer to a singular antecedent is , when the antecedent is seen as semantically plural, as in the Shaw quotation
In other words, in the Shaw quotation is syntactically singular, demonstrated by taking the singular form ; however, it is semantically plural ( go not to be killed), hence idiomatically requiring .
Linguists like Pinker and Huddleston explain sentences like this (and others) in terms of bound variables, a term borrowed from logic. Pinker prefers the terms and to and .
The word is traditionally used in two different senses:
With a morphologically singular antecedent, there are a number of possibilities, including the following:
复数代词they用于指代单数先行词的用法逐渐增多，一些研究尝试断定这种用法会不会让理解变得更“困难”。此研究之一是，《性别中性搜寻：单数they是对性别通用he在认识上的一个高效替代吗？》Foertsch与Gernsbacher著，他们发现“单数they是对性别通用he或she在认识上的一个高效替代，尤其是当先行词没有明确所指的时候”（例如anybody或者a nurse），而很少用于指代确定的一个人的时候（例如a runner I knew或者my nurse）。单数they的语句读起来“就像包含了先行词具有常规性别映像对应的有性代词的语句一样快”（例如护士用she，卡车司机用he），并且“比包含了与先行词常规性别映像的性别相反有性代词语句更快”（例如护士用he，卡车司机用she）。
代词they的单数用法和复数用法可以与代词you作比较。曾经you只能作为复数使用，对应的单数形式为thou。但是在大约1700年左右，you取代了thou，作为单数形式使用，并且动词依然使用复数形式。
quoted in , 1983, as an example of its awkwardness when referring to both sexes.
