According to the Internet medical site WebMD.com, a scaphoid fracture is, "A break in a small bone on the thumb side of your wrist. Of the eight carpal bones in your wrist, your scaphoid bone is the most likely one to break."
Why is this relevant to today's sports page?
Simple. A fracture of the scaphoid bone in North Carolina point guard Kendall Marshall's right wrist could quite possibly break the heart of every Tar Heels supporter who rightly believed Marshall was the biggest key to UNC winning its third national championship in the past eight years.
Or as former North Carolina star and current ESPN analyst Hubert Davis noted Sunday evening upon hearing the news: "It's huge. He's the one player on North Carolina you can't replace."
The good news for the Baby Blues is that Marshall's a lefty given to stunningly precise one-handed passes, especially in the open court.
The bad news is that the wrist - which he hurt in a fall against Creighton on Sunday afternoon during the Tar Heels' 87-73 third-round Midwest Regional win - began to cause much more pain as the afternoon progressed, Marshall playing at least eight minutes after the break first occurred.
In a bit of uncommonly cruel irony, North Carolina got power forward John Henson back for the Creighton contest after missing every minute of the Tar Heels' last three games. The energy upgrade from Henson's return was undeniable.
But Marshall's injury - especially should it keep him out of Friday night's Sweet 16 game against Ohio or beyond - could leave North Carolina coach Roy Williams in quite a predicament.
The Tar Heels have already spent the entire season without shooting guard Leslie McDonald due to injury, then Dexter Strickland - who could sub for Marshall - blew a knee out after Christmas.
Now this. And while nothing official will likely be forthcoming until later this afternoon, it almost certainly slows an offense that has looked all but unstoppable over the first weekend of March Madness.
In both UNC's Friday victory over Vermont and Sunday's win over Creighton, the Tar Heels looked every bit the team that was almost everyone's preseason No. 1. Yes, the defense could still be better and Harrison Barnes remains the most confounding great talent in the tournament, capable of head-scratching errors and head-shaking highlight moments in equal measure.
But Marshall may be the best open-floor passer this tournament's seen since Magic Johnson led Michigan State to the 1979 national championship over that Larry Bird guy.
Beyond that, the return of Henson gave Carolina an arguably better front line than No. 1 Kentucky, especially given Marshall's uncanny ability to find them at the right place at the right time.
Suddenly, shockingly, all that is up in the air, a stark reminder of the fragility of sports, especially when one loss leaves you done.
Of course, this tournament has been taking weird twists and turns since Thursday rolled into Friday and two No. 2 seeds (Duke and Missouri) fell to two No. 15 seeds (Lehigh and Norfolk State) in the same tourney for the first time ever.
Throw in N.C. State making the same kind of inspired run that once led the late, great Jim Valvano looking or someone to hug at the close of the 1983 championship, Florida looking positively untouchable in its two West Regional games and Friday's Sweet 16 showdown in Atlanta between Indiana and No. 1 Kentucky - the Hoosiers handing the Wildcats one of their two losses this season - and it has the promise of being one of the best tourneys ever.
So what have learned over a total of 52 games? We've learned the Big Ten was pretty good, given the four schools it still has in the Dance. We've learned the Big East may not have been as overrated as in past years - three of nine remain in the hunt after the first weekend as opposed to 4 of 19 over the past two seasons - though it did nothing to prove it deserved nine bids.
Mostly, we learned that the little guys - Lehigh, Murray State, Ohio, Norfolk State, UNC-Asheville, etc. - can really play when given the chance.
But for now we've yet to learn whether North Carolina will have its magical quarterback going forward.
Notre Dame coach Mike Brey half-joked that he'd tape Marshall up, give him a Motrin and throw him back out there.
ESPN's Davis said, "All they need him to do is defend and pass and [UNC] will be fine."
Being fine is not the same as being fantastic, but if Marshall can't play at all, it's the Tar Heel Nation that will need Motrin.