Merriam-Webster's dictionary is adding a new entry to the definition of the pronoun “they”: a way to refer to a nonbinary individual, one who identifies as neither exclusively male nor female.

It’s been a year of heightened visibility for nonbinary people, from the popularity of MTV’s “sexually fluid” season of the dating show “Are You the One?” — which counted nonbinary folks among its cast members — to the Grammy-winning artist Sam Smith’s recent decision to use gender-neutral they/them pronouns. Merriam-Webster’s addition is yet another recognition of the cultural relevance and growing acceptance of nonbinary identity, and it gives new credence to the increasingly common use of they/them pronouns.

Emily Brewster, a senior editor for Merriam-Webster, said factors like the growing practice of soliciting or giving out one’s pronouns, the growing number of people who identify as nonbinary, and the acceptance of the nonbinary “they” pronoun in a wide variety of texts all coalesced to make the new addition an obvious choice.

“We are always aiming to reflect usage,” she said. “It’s very clear that this is fully established in the language at this point.”

The nonbinary “they” is one of 530 new words and definitions already added to Merriam-Webster.com and will appear in its next printed edition, alongside words like “fabulosity” and cultural references like “dad joke.”

The singular "they" pronoun has been in use since the 1300s, according to Merriam-Webster, and it had already been included in the company’s dictionary as a gender-neutral way to refer to someone whose identity is unknown or whose existence is hypothetical. What’s new is its use as a pronoun for individuals who identify as nonbinary.

To those who are reluctant to embrace the singular "they" for grammatical reasons, Brewster pointed out that this kind of shift in the use of a pronoun has happened before. If people could adapt to it then, she said, they can learn to embrace it now.

“The word ‘you’ used to be only plural, which is why we still use the plural verb. We say ‘you are’ even though we’re only speaking to one person,” she said. “We also must adapt to the ‘they are’ for an individual person, and we can.”

Sam Brinton, head of advocacy and government affairs for The Trevor Project, an LGBTQ youth crisis prevention organization, identifies as nonbinary and uses they/them pronouns. They said Merriam-Webster’s addition of the nonbinary definition will hopefully help bolster a better understanding of nonbinary identity.

"My day-to-day life consists of helping those around me understand that my pronouns, they and them, are a part of my identity,” Brinton wrote in an email to NBC News. “To have Merriam-Webster so openly educate others on the simplicity of the nonbinary use of they and them pronouns is going to make each coming day a little easier for thousands if not millions of LGBTQ youth.”

On Twitter, reactions were a predictable mix of excitement from the LGBTQ community and allies, and disdain from grammar purists and those who do not support gender-nonconforming identities.

For the record, nonbinary humans have been around since there have been humans. And although we ARE DELIGHTED for language to “officially catch up,” it doesn’t change our validity because we have always been valid💛💛😇 https://t.co/XTMIoG328B — jeffrey marsh (@thejeffreymarsh) September 18, 2019

What great news!



Shout out to all our non-binary fam in the world, and the activists who’ve worked hard to let us celebrate the full spectrum of humanity 🏳️‍🌈 https://t.co/BkpdVPleNe — Alexandria Ocasio-Cortez (@AOC) September 18, 2019

Brewster said she’s glad nonbinary people feel validated by the dictionary’s decision, but she stressed that Merriam-Webster doesn’t legitimize language — people do, and the singular, gender-neutral “they” has been a legitimate term in that sense for a long time.

“The word exists. You don’t actually need a dictionary to legitimize the words,” she said. “But of course if it can serve that function I’m happy for it to do so.”

Follow NBC Out on Twitter, Facebook & Instagram