ABC News September 18, 2019

Merriam-Webster adds 'they' as nonbinary pronoun to dictionary

WATCH: Nonbinary pronoun 'they' added to Merriam-Webster dictionary

Merriam-Webster has added another definition for the word "they" that can be used to refer to a single person whose gender identity is nonbinary, or someone who expresses a gender identity that is neither entirely male or entirely female.

The reference book company used the word as an example in this sentence: "They had adopted their gender-neutral name a few years ago, when they began to consciously identify as nonbinary."

(MORE: Hangry is officially a word in the Oxford English Dictionary)

In a post on its website, the company acknowledged that "they" has been used to refer to a single person since the 13th century and that the development of the singular use mirrors the development of the singular use of "you" from the plural "you."

Joanne K. Watson/Merriam-Webster via Getty Images
In this September 23, 2016, file photo provided by Merriam-Webster, Merriam-Webster's Collegiate Dictionary and mobile website are displayed in Springfield, Mass.

Merriam-Webster noted that, while some may say the use of "they" in a singular form is ungrammatical, people have used it to describe someone whose gender is unknown for a "long time," although the nonbinary use of the word is "relatively new."

(MORE: Yowza! 1,000 words were just added to Merriam-Webster's dictionary)

"Much has been written on they, and we aren’t going to attempt to cover it here," the post stated.

Merriam-Webster also announced the addition of 530 new words on Tuesday, including deep state, dad joke and escape room.

(MORE: Merriam-Webster adds 'genderqueer,' 'genderfluid' and gender-neutral title 'Mx' to dictionary)

New abbreviations include "vacay," short for vacation, "sesh," short for session and "inspo," short for inspiration.