an imperfection in a crystal's lattice structure, either a missing atom or ion creating a vacancy in the lattice or an extra atom or ion between two normal lattice points creating an interstitial.
Moot Point vs. Mute PointYou may have heard coworkers or acquaintances refer to an inconsequential or irrelevant point as a moot point, or maybe you’ve heard mute point instead. Fans of the TV show Friends may have heard a third variation: moo point (because, according to Joey, a cow’s opinion doesn’t matter). But which expression is correct, and what exactly does it mean? The correct phrase is moot point. …
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British Dictionary definitions for point defect
an imperfection in a crystal, characterized by one unoccupied lattice position or one interstitial atom, molecule, or ion
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012