The Little Book of Linear Algebra: A Beginner's Guide to Core Concepts

A scalar is a single numerical quantity, most often taken from the real numbers, denoted by $\mathbb{R}$

Scalars are the fundamental building blocks of arithmetic: they can be added, subtracted, multiplied, and, except in the case of zero, divided

In linear algebra, scalars play the role of coefficients, scaling factors, and entries of larger structures such as vectors and matrices

There is hardly any theory which is more elementary than linear algebra, in spite of the fact that generations of professors and textbook writers have obscured its simplicity by preposterous calculations