Ключевые слова: abstract, advertising, aged, alarm, alert, background, black, blackboard, board, business, chalk, chalkboard, class, classroom, clock, college, communication, concept, dirty, drawing, educate, education, erase, exam, grunge, information, knowledge, learn, learning, lesson, message, note, old, reminder, ring, school, scratch, sign, space, stains, student, study, studying, surface, symbol, teach, teacher, texture, time, unclean, university, used, vintage, wall, white,