The Set of Natural Numbers:

    Figure 2:  The Natural Number Symbol that I scripted in SVG. The Natural Number symbol is a blackboard boldface ‘N’.

    Figure 2:  The Natural Number Symbol exported as a PNG file.

The set of Natural numbers can refer either to the set of non-negative integers, i.e.:

{0, 1, 2, 3, 4, ...}

or to the set of positive integers, i.e.:

{1, 2, 3, 4, 5, ...}

The term, ‘natural numbers,’ refers to quantities observed in nature. One can have two apples; three pears or five bananas; however one cannot have π bananas or minus-three[1].  pears:

π ∉ ℕ

.

As we observe, above, π is not an element in the set of natural numbers.

-3 ∉ ℕ

.

Minus Three is not an element in the set of Natural numbers.

[1].  In America, they would generally term -3 ‘negative three’

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