MENLO PARK, California (AP) — You don’t have to be just male or female on Facebook anymore. The social media giant is adding a customisable option with about 50 different terms people can use to identify their gender as well as three preferred pronoun choices: him, her or them.

Facebook said the changes, shared with The Associated Press before the launch yesterday, initially cover the company’s 159 million monthly users in the US and are aimed at giving people more choices in how they describe themselves, such as androgynous, bi-gender, intersex, gender fluid or transsexual.

Facebook plans to take it global after working with activists abroad to come up with terms appropriate in other countries.

“There’s going to be a lot of people for whom this is going to mean nothing, but for the few it does impact, it means the world,” said Facebook software engineer Brielle Harrison, who worked on the project and is undergoing gender transformation from male to female. She said she was changing her Facebook identity from Female to TransWoman.

“All too often transgender people like myself and other gender-nonconforming people are given this binary option, do you want to be male or female? What is your gender? And it’s kind of disheartening because none of those let us tell others who we really are,” she said. “This really changes that, and for the first time I get to go to the site and specify to all the people I know what my gender is.”

Facebook, which has 1.23 billion active monthly users around the world, also allows them to keep their gender identity private and will continue to do so.

The Williams Institute, a think tank based at the University of California, Los Angeles, estimates that at least 700,000 individuals in the US identify as transgender, an umbrella term that includes people who live as a gender different from the one assigned to them at birth.

The growing transgender rights movement in the US has been led by veteran activists and young people who identify as transgender at younger ages. The Human Rights Campaign last year found that 10 per cent of the 10,000 lesbian, gay, bisexual transgender youths it surveyed used “other” or wrote in their own gender terms.

“Over the past few years, a person’s Facebook profile truly has become their online identity, and now Facebook has taken a milestone step to allow countless people to more honestly and accurately represent themselves,” HRC President Chad Griffin said. “Facebook’s action is one that I hope others heed in supporting individuals’ multifaceted identities.”

The change to the gender selection option is seen as a major step toward acceptance for people who don’t self-identify as male or female, but the high-profile development seemed senseless to those who believe in two genders, no more.

“Of course Facebook is entitled to manage its wildly popular site as it sees fit, but here is the bottom line: It’s impossible to deny the biological reality that humanity is divided into two halves: male and female,” said Jeff Johnston, an issues analyst for Focus on the Family, an influential national religious organisation.