This actually happened in one of the initial lectures in an introductory course in linear algebra. This was an altogether new experience for us to get acquainted with abstract way of thinking. So the teacher said -"Let a, b and c be three linearly independent vectors in the vector space R^n." A guy interjected -" Sir, can you be more concrete?" "Ok"-said the professor and continued - ""Let alpha, beta and gamma be three linearly independent vectors in R^n".