Most of us see the range of men’s sexualities as pretty limited. They’re straight, they’re gay, or if they’re anything in between, they’re bi.

But these clean and tidy categories don’t seem to suit many of today’s young men, explains Ritch Savin-Williams, director of the Sex & Gender Lab at Cornell University. He began noticing changes in the data trends on men’s self-reported sexual identities, which ultimately inspired his book, “Mostly Straight: Sexual Fluidity Among Men,” released last month on Harvard University Press.

A U.S. government poll published earlier this year found that 6 percent of 18- to 24-year-olds and 3.5 percent of 25 to 44-year olds marked their sexual attractions as “mostly opposite sex.”

If Savin-William’s estimates are correct and as much as 9 percent of the total US male population is “mostly straight,” that’s millions of men deviating from the traditional sexual norms.

However, when the government study’s “mostly straight” men were forced to choose among the big three orientations — straight, gay or bisexual — the vast majority chose “straight,” because bisexual seems far too queer to describe them.

In his book, Savin-Williams interviews 40 men who identify as “mostly straight.” These men admittedly adore women, yet often feel a slight sexual or romantic desire for other men. They might find themselves intensely admiring another good-looking fellow, or recognizing intense feelings of friendship with a buddy that sometimes seems to stretch beyond platonic.

The typical reaction to these men’s confessions is the assumption that they’re closeted gays. They’re not, Savin-Williams says. Instead, they’re allowing themselves to recognize male sexuality as fluid, a freedom generally only granted to women.

They’re secure in their masculinity while also recognizing the possibility of experiencing far more. This doesn’t overshadow their love of women, nor necessarily translate into actual same-sex behavior. “He feels his same-sex sexuality internally more than he lives it externally,” Savin-Williams writes.

The idea of sexuality along a spectrum for men and women is nothing new. Nearly 70 years ago, Alfred Kinsey published his famous research indicating that sexual orientation falls along a continuum.

Generally, the younger the generation, the more flexible men tend to be with their sexual labels. Millennials, Savin-Williams has observed, tend to have greater sexual knowledge, curiosity and freedom for exploration than older generations. “Identifying as mostly straight is now largely possible because the millennial generation is adding new complexity to sexual and romantic relationships,” he writes.

It's also possible that the “mostly straight” identity might come from the increasing acceptance of sexual diversity allowing youngsters to defy convention and admit: they’re willing to make exceptions for exceptionally hot people.

After all, young people reject labels, live outside boxes and change from day to day. Saying that they're "mostly straight" could just be one way of saying: I'm not so easy to pin down.