Q.  What are the criteria for designating a shot an unforced error?
-Rolland LeBlanc, Saratoga Springs, NY

A.  For this one we deferred to the industry expert, the renowned Dr. Leo Levin of IDS Sports, who does or has done statistics for all of the major tennis tournaments and then some. He's also the person who came up with the term "unforced error" in 1982. Here's what he said.

"By definition, there are only three ways to end a point - with a winner, forced error or unforced error. The idea of an error being either forced or unforced is to place the blame for the error - who is responsible for the missed shot?  Was the error forced by the aggressive play of the opponent or was it unforced, just a mistake by the player who hit the shot?"

"This is how we train our staff to judge an unforced error. An unforced Error is when the player has time to prepare and position himself or herself to get the ball back in play and makes an error. This is a shot that the player would normally get back into play. The real keys here are time and position.  When the opponent takes away time by hitting the prior shot with extra pace this can result in a forced error.  Also, when the opponent forces the player out of position with placement (depth and/or angle) this can result in a forced error."

"As examples, most missed returns of first serves are considered to be forced errors - forced by the pace and placement of the opponent's serve. Many, if not most return errors against second serves, would be unforced errors since most second serves are just means to get the point started and do not put extra pressure on the receiver."

"Other examples, most passing shot attempts that fail would be classified as forced errors, forced by the opponent's aggressive play (the exception would be when an opponent hits a weak approach and the player has time to setup and then misses the shot, that would be unforced).  Most approach shot errors would be unforced because the player is attempting to hit an aggressive shot and misses."

"Another way to look at it is this. Would you classify the prior shot as "weak" or just "in play" Or would you say it was "forcing" or "aggressive"? An error made off of a "weak" or "in play" shot would be unforced.  An error resulting from a "forcing" or "aggressive shot" would be forced."

"By definition double faults are unforced errors."