Tim Rusthoven added 13 points for William & Mary (6-3).
Ahead 32-31 early in the second half, Thornton made a layup and connected from 3 to push the Tribe's lead to six, 37-31, with 17:43 left in the period.
Radford (5-5) trailed by single digits most of the second half until Rusthoven's tip-in and two free throws extended William & Mary's lead to 10, 57-47 with 3:36 left to play.
Kion Brown led Radford with 13 points and nine rebounds.
High school junior Zach Brown, a 7-footer from Miami, has rescinded his commitment to UConn, sources told ESPN.
Reserve center Akolda Manyang has been charged with felony aggravated assault after being accused of punching a man in the face without provocation.
Should the 76ers take Ben Simmons No. 1? What if they get the Lakers' pick, too? And how does the rest of the top 10 shake out? Our Insiders run their latest mock draft, with Philly on the clock.