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America's oldest dictionary Merriam Webster has also recently added the word 'they' as a non-binary pronoun to its website.

Gender-neutral pronouns are defined by the LGBT Resource Centre as providing an identity for a singular person who does not identify as he/him or she/her.

Now, in English, the word "they" is used as a gender-neutral singular pronoun - even though some critics argue that "they" should really only be used to refer to plural nouns.

But these identifiers are nothing new and have actually been used throughout the history of literature.

Examples of the singular "they" being used to describe someone features as early as 1386 in Geoffrey Chaucer's The Canterbury Tales and also in famous literary works like Shakespeare's Hamlet in 1599.

"They" and "them" were still being used by literary authors to describe people in the 17th Century too - including by Jane Austin in her 1813 novel Pride and Prejudice.

While these pronouns weren't used historically to define people as gender neutral, 'they' was used to specify a role being undertaken by a person.

"You could say that somebody was say, a teacher, but you didn't know whether that teacher was male or female," Dr Emma Moore, a professor of linguistics at the University of Sheffield, tells Radio 1 Newsbeat.