A scalar is a single number. Scalars are usually written in italics with lowercase variable names.

$$s = 1.7$$

In Python, a scalar can be represented as a floating point variable.

s = 1.7
print("Scalar {} has type {}".format(s, type(s)))

Scalar 1.7 has type <class 'float'>

Source: https://github.com/maxbartolo/ml-index/blob/master/01-basic-math/01-linear-algebra/01-scalars.ipynb