[Next: Matrices, dot products, and matrix multiplication](https://forum.azimuthproject.org/discussion/2479/matrices-dot-products-and-matrix-multiplication)

* * *

There are various choices for what a 'number' means:

* \\(\mathbb{N}\\) = set of all natural numbers = {0, 1, 2, ...}

* \\(\mathbb{N^+}\\) = counting numbers = {1, 2, ...}

* \\(\mathbb{Z}\\) = integers = {..., -3, -2, -1, 0, 1, 2, 3, ...}.

* \\(\mathbb{Q}\\) = rational numbers = all fractions p/q for integer p,q

* \\(\mathbb{R}\\) = real numbers = all limits of infinite sequences of rationals

* \\(\mathbb{C}\\) = complex numbers = all a + bi for real a,b

* * *

There are various choices for what a 'number' means:

* \\(\mathbb{N}\\) = set of all natural numbers = {0, 1, 2, ...}

* \\(\mathbb{N^+}\\) = counting numbers = {1, 2, ...}

* \\(\mathbb{Z}\\) = integers = {..., -3, -2, -1, 0, 1, 2, 3, ...}.

* \\(\mathbb{Q}\\) = rational numbers = all fractions p/q for integer p,q

* \\(\mathbb{R}\\) = real numbers = all limits of infinite sequences of rationals

* \\(\mathbb{C}\\) = complex numbers = all a + bi for real a,b