When Is a Number, Not a Number?
What numbers are not numbers? In some cases, as discussed below, information
is represented with digits but does not represent a numeric value to be used in
arithmetic operations. Basically, there are three types of numbers in general
use: symbols, ordinals, and cardinals.
Symbols
Many of the numbers we use every day are not numbers at all. They are
identifiers of some sort, not representing quantities or ranks. Here are the
most common examples:
·
Phone
Numbers:
These are now almost entirely digital. Years ago, shorter numbers included an
alphabetic prefix. For example, an old phone number might have been “LI5-7624”,
where "LI" stood for "Lincoln." Now, area codes and country
codes are required for calls between cities and countries, respectively.
·
Identification
Numbers:
These include Social Security numbers, student numbers, serial numbers, part
numbers, etc. They are digital identifiers for which no mathematical operations
can be performed.
·
Credit
Card Numbers:
These are among our most important “numbers though not numbers.” Typically,
they have 16 digits, along with a special three-digit security code visible
only to the physical cardholder.
·
Vehicle
Identification Numbers (VINs): These are 17-character codes containing
mostly digits and some letters. Similarly, router ID numbers are usually formed
with fewer digits.
·
Postal
(ZIP) Codes:
These are five-digit codes used for mail delivery. For example, my ZIP code is
77840. ZIP codes start from 00501. The ZIP+4 system extends the standard
five-digit ZIP code with four additional digits to improve mail delivery
accuracy and speed.
·
Addresses: An address might
be something like 2932. Doubling it or taking its square root has no meaning
relative to the address. For apartment complexes, the address would include
"Street address + Building number + Unit number," none of which make
sense for arithmetic operations.
It may seem odd, though true, that many of the numbers in your life are not
numbers at all, but merely symbols. Our next category, ordinals, are not truly
numbers either, but they do have an "ordering," making them closer to
actual numbers, the cardinals.
Ordinals (or Ranks)
These are rankings: first, second, third, and so forth, often abbreviated as
1st, 2nd, 3rd, etc. They are not suitable for arithmetic. For example, you
cannot add 1st and 2nd to get anything meaningful. Consider tennis rankings:
the rank is an ordinal number based on tournament points scored over a year.
Arithmetic does not apply, but you can consider the number of those ranked
between various rankings.
Ordinals are crucial when ranks are important, such as in sports, stocks,
wealth, and all forms of measurable excellence where there is a "top
dog." In the animal kingdom, the alpha leader (1st) of any pack makes
decisions, eats first, and controls reproductive activities. The matriarch/patriarch of a family or herd is the de
facto leader, controlling important decisions. Similarly, business
operations, organized religions, and governments are based on an ordinal
hierarchy. Military organizations and operations are strictly hierarchical
(ordinal) by nature.
While ordinals are not truly numbers in the sense of arithmetic, they have
supreme importance in organized society and all organizations. Let us now turn
to the “real” numbers on which all mathematics and our daily lives depend.
Cardinals
Cardinals represent quantities, like apples, volts, dollars, etc. These are
the only numbers suitable for arithmetic to obtain meaningful values. For
instance, you can add two apples to three apples to get five apples, but you
cannot add two apples to three oranges meaningfully. In school, math class
typically deals with cardinals without tags, i.e., abstract numbers.
Cardinals can extend to fractions, decimals, and real numbers. Infinity (∞)
has unique arithmetic properties such as ∞ + ∞ = ∞. Cardinals can be abstracted
to new objects such as groups, rings, and fields, which have arithmetic-like
properties. These are very useful in modern living, though we rarely see them.
One particular number system, the binary system, is highly useful in computing
machines.
Cardinals, rationals, and reals form the class of numbers that truly are the
numbers we love – and need.
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