penumbra -- Sam

pe·num·bra  (p-nmbr) n. pl. pe·num·brae (-br) or pe·num·bras 1. A partial shadow, as in an eclipse, between regions of complete shadow and complete illumination. See Synonyms at shade. 2. The grayish outer part of a sunspot. 3. An area in which something exists to a lesser or uncertain degree: "The First Amendment has a penumbra where privacy is protected from governmental intrusion" (Joseph A. Califano, Jr.) 4. An outlying surrounding region; a periphery: "Downtown Chicago and its penumbra also stand rejuvenated"(John McCormick). [New Latin pnumbra : Latin paene, almost + Latin umbra, shadow.] pe·numbral, pe·numbrous adj.

The American Heritage® Dictionary of the English Language, Fourth Edition copyright ©2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

Sam concentrated in the mid-day sun so that the tennis ball's penumbra did not distract him from his shot.