“A pronoun like ‘they’ is one of the building blocks of the language,” Mr. Sokolowski said. “But with the nonbinary usage, people are sensing that it means something new or different, and they are going to the dictionary. When you see lookups for it triple, you know that ‘they’ is a word that is in flux.”

Many Americans, especially older ones, stumble over the use of “they” as a singular pronoun. “For those who haven’t kept up, the complaint is this,” Merriam-Webster wrote in an earlier blog post on the topic. “The use of they as a gender-neutral pronoun (as in, ‘Ask each of the students what they want for lunch.’) is ungrammatical because they is a plural pronoun.”

But for nonbinary individuals who identify as a gender other than male or female, being referred to as “he” or “she” is inaccurate. Over a third of Americans in their teens and early 20s know someone who uses gender-neutral pronouns, according to a Pew Research survey conducted last fall. That is double the number of those in their 40s, and triple those in their 50s and 60s.

Efforts to destigmatize other gender identities have sparked the disclosure of pronouns on social media profiles and email signatures. Some state and city governments have recently added an “X” option for nonbinary genders on state identification documents, which used to be limited to the options “M” and “F.” And amid efforts this year in at least six states to make the practice law, state legislators have been grappling with the singular “they,” The New York Times reported.

Merriam-Webster added the singular “they” for a person with a nonbinary gender as a definition of the word in its dictionary, noting that the use of the singular “they” to refer to nonbinary individuals is increasingly common in published, edited text, as well as on social media.