Certainly many usage guides have advised against use of this " singular they " on various "logical" grounds.
Nevertheless, singular they has long been part of the English language, and there are various posts on Language Log giving examples of it being used in the Bible , by Shakespeare , by the president , by the Canadian Department of Justice , etc. .
The Cambridge Grammar of the English Language 's coauthor Geoff Pullum (a frequent Language Log contributor) calls the idea that they must never occur with a singular antecedent a myth .
There is no shortage of usage "experts" who advise against it, as the other answers in the question should make clear (though these days their reasoning tends away from a simple "it's wrong" towards something more defensive–"some
people will think it's wrong, so avoid it").
But despite them, use of singular they occurs at all levels of the language, both spoken and written, informal and formal.
It's not ungrammatical per se on the basis of analysis of actual usage using reasonable linguistic methods.
But use it at your own risk of being criticized by the self-righteous but misinformed.
english.stackexchange.com/users/39/nohat
Up until very recent times the natural answer would have been "Anyone who loves the English language should have a copy of this book in his bookcase", because "his" was also a gender-neutral pronoun.
It turned out, however, that "his" could only function as a gender-neutral pronoun if it were a plot by the patriarchy or something, so we're in the process of trying out alternatives.
I've heard serious proposals to substitute "their", "his or her", "her", "its", and even "hisorher".
Of those alternatives, I use "their" because it sounds the most natural to me, but usually I avoid pronouns altogether, as in, "This book should be book in the bookcase of anyone who loves the English language."
That style has the additional advantage of making you sound formal and pedantic.
english.stackexchange.com/users/152/Taldaugion
Second one (for writing purpose), if I believe the " THEY/THEIR (SINGULAR) " article.
A good general rule is that only when the singular noun does not specify an individual can it be replaced plausibly with a plural pronoun :
“Everybody” is a good example.
We know that “everybody” is singular because we say “everybody is here,“ not “everybody are here” yet we tend to think of “everybody” as a group of individuals, so we usually say “everybody brought their own grievances to the bargaining table.”
“Anybody” is treated similarly.
However, in many written sentences the use of singular “their” and “they” creates an irritating clash even when it passes unnoticed in speech.
It is wise to shun this popular pattern in formal writing .
english.stackexchange.com/users/110/VonC
I have gone to using their instead of the increasingly awkward him/
her in all but the most formal of my writings.
His or her is sounding very contrived, and it is no better to substitute her for him than to have him as the gender neutral pronoun.
The use of their is increasingly common and should simply be accepted by grammarians, though it will probably take a century or so before the high and mighty accept this increasingly common usage.
english.stackexchange.com/users/17082/John Heckers
See here or here or here .
Executive summary:
His/her is to be avoided.
english.stackexchange.com/users/15299/John Lawler
In a business English course at WVU in 1987, I was taught to avoid the sexist language/agreement problem by making the subject plural: Anyone All the people who love the English language should have copies of this book in their bookcases.
english.stackexchange.com/users/20482/Fuhrmanator
In these days of exaggerated care for egalitarianism it is always a conundrum whether to use "his", "her" or "their".
And perhaps we should be concerned about egalitarianism.
On the other hand, the traditional use of the masculine gender to stand in for both sexes still doesn't seem too outré to me.
As a guy, perhaps I am missing something.
What I would do, if I were writing technical works, would be to write one with a masculine user, and the next time do it for a feminine user.
Leave each work (whether an essay or a book) consistent as to gender of the subject user.
Alternatively, if you are a female writer, your user should always be female; and if a male writer, then male user.
Lot's of choices out there!
Try to offend as many people as possible.
english.stackexchange.com/users/20156/Cyberherbalist
Is this sentence grammatically correct?   Anyone who loves the English language should have a copy of this book in  their  bookcase.   or should it be:   Anyone who loves the English language should have a copy of this book in  his or her  bookcase.
Is it correct to use "their" instead of "his or her"?
english.stackexchange.com
<grammaticality><pronouns><personal-pronouns><gender><singular-they>
english.stackexchange.com/questions/192
english.stackexchange.com/users/30/Edward Tanguay
It is true that many usage guides advise against using the "singular they", however, the use of the singular "they" occurs at all levels of the language. Therefore, there is no clear rule as to whether this is acceptable or not. Views vary - some people regard the use of the plural as informal and incorrect but it is an increasingly widespread and accepted form in this context.
It is true that many usage guides advise against using the "singular they", however, the use of the singular "they" occurs at all levels of the language. Therefore, there is no clear rule as to whether this is acceptable or not. Some grammarians have advised against use of thie" singular  they " on various "logical" grounds, but it is not ungrammatical per se on the basis of analysis of actual usage using reasonable linguistic methods. Sngular  they  has long been part of the English language, with examples of it being used  in the Bible ,  by Shakespeare ,  by the president ,  by the Canadian Department of Justice ,  etc. Use of singular  they  occurs at all levels of the language, both spoken and written, informal and formal.  The use of  their  is increasingly common and should simply be accepted by grammarians, though it will probably take a century or so before the high and mighty accept this increasingly common usage. His/her  on the other hand should be avoided.
It's not ungrammatical on the basis of analysis of actual usage using reasonable linguistic methods. However, some usage guides have advised against use of a " singular  they " on various "logical" grounds. It is generally agreed that use of the singular "their" is not grammatically incorrect, although there do exist language guides that advise against it.
No - this is a widespread usage and has been for a very long time, however ungrammatical it may appear. It is alright - but can often be avoided by changing the sentence structure. It is a popular form that should be avoided in formal writing. The use of there is increasingly common way to avoid his or her. I was taught specifcally to use plural pronouns as a way of avoiding sexist language. You can still use the masculine gender as a gender-neutral form.
Some grammarians have advised against use of thie" singular  they " on various "logical" grounds, but it is not ungrammatical per se on the basis of analysis of actual usage using reasonable linguistic methods. Sngular  they  has long been part of the English language, with examples of it being used  in the Bible ,  by Shakespeare ,  by the president ,  by the Canadian Department of Justice ,  etc. . Use of singular  they  occurs at all levels of the language, both spoken and written, informal and formal.   The use of  their  is increasingly common and should simply be accepted by grammarians, though it will probably take a century or so before the high and mighty accept this increasingly common usage. His/her  on the other hand should be avoided.
There are certainly language usage guides that advised against using 'their' in the singular form. This particular use of 'their' is not grammatically incorrect.