Jeff Bezos is going to space today, but whether that makes him an astronaut is open to interpretation.

Why it matters: Bezos and his billionaire rival, Richard Branson, are hoping to lure wealthy customers into space tourism, in part, with the promise of becoming astronauts — but the definition of who is considered an astronaut isn't clear-cut.

• "There is going to be a segment of the population that's waiting in line to ride [these suborbital rockets] because they have dreamt of being an astronaut their entire lives, and to be told they're not an astronaut would ruin the experience for them," space historian Robert Pearlman told me.

How it works: The FAA, U.S. military and NASA all have different definitions of what it means to be designated as an "astronaut" and none of them fit perfectly with the way Bezos' Blue Origin or Branson's Virgin Galactic are doing business.

• NASA and the military's definitions have specific criteria and are reserved for their employees.
• In order to receive commercial astronaut wings you have to be an employee of the company performing the launch, certified by the FAA and be a crewmember performing some kind of job during the mission.

The intrigue: It's possible that, by that definition, Branson will receive FAA commercial astronaut wings, while Bezos won't.

• Virgin Galactic classified Branson as a crew member, whose job was to evaluate the astronaut experience. The Blue Origin vehicle that will carry Bezos today, however, is autonomous — no one onboard needs to act as a pilot or flight crew.
• Oliver Daemen, the 18-year-old paying customer on the Blue Origin flight, definitely won't get official FAA wings, because he's paying for the trip.

Between the lines: Fewer than 600 people have flown to space in history, and most of them have been government employees paid to explore, but this new era of commercial spaceflight opens up that opportunity — to see Earth against the blackness of space — to many more people.

• Virgin Galactic uses the American-recognized boundary for defining where space begins — at 50 miles up. Blue Origin's vehicle will take its passengers past the Karman Line, the international boundary for where space begins, at about 62 miles above the planet.
• Virgin Galactic awarded its own wings to its astronauts after Branson and his fellow crewmembers came back down to Earth. It's not yet clear whether Blue Origin will award its own astronaut wings, too.

What to watch: All of these questions about who qualifies as an astronaut could become moot if the market for space tourism truly takes off.

• If enough people fly and prices go down enough, it's possible that the term "astronaut" will go the way the term "aviator" did when commercial air travel became available to most members of the public.
• Today, "aviator" is reserved for a select group of people that are performing risky flights, pushing the bounds of what's possible. In the future, "astronaut" might become a similar designation, Pearlman said.

"No one had to step in and say, 'You're not an aviator,' and that's exactly what's going to happen with 'astronaut'," Pearlman said. "When 'astronaut' is no longer a bragging status, then it will resume being used only by those people who are going into space for exploration or if it's their job."