Merriam-Webster has chosen "they", the preferred pronoun of people who identify as non-binary, as its word of the year for 2019.
It follows changes made by the American English dictionary in September to include references to non-binary useage in its entry for "they".
The dictionary states that "they" can be "used to refer to a single person whose gender is intentionally not revealed" or "whose gender identity is nonbinary".
Merriam-Webster, which dates back to 1828, said the winner of its word of the year was determined by data, with searches for "they" rising by 313% in the last year.
It said there were several particularly noticeable spikes in searches throughout 2019. The first was during Paris Fashion Week in January, when non-binary model Oslo Grace, walked the runway, and again in April when US congresswoman Pramila Jayapal made a statement about her child being gender-nonconforming.
Searches for the pronoun spiked again in June during Pride celebrations, the dictionary said.
Non-binary people do not identify as male or female and commonly choose to be referred to as 'they' or 'them' instead of 'he' or 'she'.
A number of celebrities have publicly identified as non-binary, including British singer Sam Smith and #MeToo campaigner Rose McGowan. Smith has asked to be referred to as 'they/them'.
Emily Brewster, senior editor at Merriam-Webster, said in a statement: "Pronouns are among the language's most commonly used words, and like other common words (think go, do, and have) they tend to be mostly ignored by dictionary users.
"But over the past year or so, as people have increasingly encountered the nonbinary use, we've seen searches for 'they' grow dramatically."
She continued: "People were clearly encountering this new use and turning to the dictionary for clarity and for usage guidance."
Merriam-Webster is not the only dictionary to have expanded its definition of 'they'. Collins has also changed its entry to state, "You use they instead of 'he or she' to refer to a person without saying whether that person is a man or a woman."