material used by a teacher to supplement classroom instruction or to stimulate the interest of students.
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British Dictionary definitions for teaching aid
any device, object, or machine used by a teacher to clarify or enliven a subject
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