You don't have to be just male or female on Facebook anymore. The social media giant is adding a customizable 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 initially cover the company's 159 million monthly users in the U.S. 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 told The Associated Press she was changing her Facebook identity from female to transwoman.

"All too often," she said, "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. 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 1.15 billion active monthly users around the world, also allows users to keep their gender identity private and will continue to do so.

In a statement to Al Jazeera, Facebook spokesman Slater Tow said the company sees the move as "one more way we can make Facebook a place where people can express their authentic identity."

The change to the gender-selection option is seen as a step toward acceptance for people who don't self-identify as male or female, but the high-profile development was criticized by an influential conservative religious organization.

"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.

Masen Davis, executive director of the Transgender Law Center, said it may be hard for some people to understand the importance of having the ability to select from multiple genders online. But he said many transgender people will be thrilled with the change.

"We applaud Facebook for making it possible for people to be their authentic selves online," he said.

In the past decade, the transgender movement has become much more organized and outspoken, demanding the kind of civil rights and respect already sought by gay activists. During this time, the transgender category has been growing beyond transsexuals to encompass a variety of gender identities.

The move by Facebook came after years of lobbying from users, some of whom started Facebook pages to petition for the change. Google+ offers male, female and "other" as choices, but transgender advocates said Facebook's many specific options put the platform well ahead of any other online community. About 1 percent of Google+ users identify as other.

At this point, Facebook targets advertising according to male or female genders. For those who change to something neutral, ads will be targeted based on the pronoun they select for themselves. Unlike getting engaged or married, changing gender is not registered as a "life event" on the site and won't post on timelines. As a result, Facebook said advertisers cannot target ads to those who declare themselves transgender or recently changed their gender.

Al Jazeera and The Associated Press