The Merriam-Webster dictionary recently added 533 new words and meanings, including a new meaning for the word “they.” The pronoun can now be used in reference to a “single person whose gender identity is nonbinary.”

Of course, “they” has been used in this way for a long time without being in the dictionary. But the move by Merriam-Webster, announced via Twitter on Tuesday, lends legitimacy to a term that is liberating for many nonbinary people who don’t identify with traditionally male and female pronouns.

Inclusive language is evolving, with many organizations across the country making room in the language they use for nonbinary “they/them.” Several journalism style guides have adopted new policies on gender-neutral pronouns in recent years. The Associated Press began permitting the singular “they” in 2017 in certain cases. The Washington Post has recognized gender-neutral “they/them” as of 2015.

In a blog post, Merriam-Webster points out that “they” has been consistently used as a singular pronoun since the late 1300s. It gives an excerpt from a letter written by Emily Dickinson in 1881 in which she uses “they” in reference to a singular person and points out that even sticklers use this pronoun in this way in casual speech. So this isn’t a new phenomenon, no matter what English teachers might say.

Language reflects the society in which it operates. If people begin to develop their way of thinking about gender, as we have lately in the United States, they’ll develop new ways of expressing themselves. While many might look to dictionaries as the ultimate authority on how that language should operate, they’re not meant to be an unbreakable set of rules. Dictionaries are a snapshot of how a language is used at a particular time — those compiled centuries ago contain words and aspects of language that haven’t been used in years but were used at the time they were written.

And right now, the idea and use of “they/them” as nonbinary is becoming more and more mainstream. Many high-profile people are coming out as nonbinary, including Sam Smith, who tweeted Friday that they decided to go by these pronouns.

“Today is a good day so here goes,” they tweeted. “I’ve decided I am changing my pronouns to THEY/THEM after a lifetime of being at war with my gender I’ve decided to embrace myself for who I am, inside and out…”

This recognition by Merriam-Webster might seem insignificant, but it’s part of the ongoing social shift towards more openness and inclusivity towards people who don’t conform with traditional gender labels and norms. It helps legitimize a linguistic practice of referencing individuals who don’t feel their language properly represents them that has often been called ungrammatical.