Around 1200 AD, Hindu numerals were
introduced into Europe.

At which point they began to be
referred to as Arabic numerals

and began increasing in popularity.

Through the years, Arabic numerals
have spread across the entire globe

and, since the 15th century,
have become the most commonly

used numeral system in the world.

However, previous to it's introduction
in Europe, the Arabic numeral system

could only be found in a few locations
and was referred to as the

Hindu numeral system.

At that time there were wasn't a very
universal numeral system but in Europe

the most commonly used numeral system
was the Roman numeral system.

Which, as the name suggests
was invented in Rome.

They were created around the time
Queen Esther was born. About 500 B.C.

The modern Roman numeral system
we use today is composed primarily

of 7 letters.

I, V, X, L, C, D, and M.

I is equal to 1, 

V is equal to 5,

X is equal to 10,

L is equal to 50,

C is equal to 100,

D is equal to 500,

and M is equal to 1000.

If you're like me and have trouble
remembering what each of the

numerals represents,
just remember that I looks

like a 1,

V is five which is evenly divisible

(wait no it's not),

X kinda like two V's put together(ish),

L is for “Lost in Roman numerals 50 times”,

C is for century (which is 100 years),

D is for “Didn't remember 500 was a D”,

and M is for millennium (which is 1000 years).

If you still can't remember them
than maybe this will make it a little worse.

If you need to write a number that's not
one of the primary letters,

like for example 149,

you add larger numbers onto the end
and subtract smaller numbers

from the beginning.

So 149 in Roman numerals
would be CXLIX.

Which reads out as
100+(50-10)+(10-1).

X is a smaller number than L
so it subtracts 10 from 50 leaving 40.

I is smaller than X so it
subtracts 1 from 10 leaving 9.

Both combined equals 49 and
adding the C gives us 149.

There is a major problem
with this system though.

Actually,

there's far more than one.

First,

there's not actually one way to
write numbers.

999 for example can be written as
CMXCIX,

LMVLIV,

VMIV,

or simply IM.

All of which equal 999 but are
completely different.

There are also some other ancient
examples which are even more odd.

Like 1613 being written as XVIXIII
which literally means 16, 13

but it really makes no sense
unlike the standard form which is MDCXIII.

Another issue is that Roman numerals
take up a lot of space.

While 1000 is just a simple M,
as soon as you go down one digit

to 999

you suddenly have CMXCIX
which is far longer than M.

And while 1000 is M,
3888 is

MMMDCCCLXXXVIII.

In Arabic numerals those two
numbers are the exact same length,

but in Roman numerals one is
15 times longer than the other.

Sometimes you can avoid this,
like with 3999 for example.

You could either write MMMCMXCIX
which is the standard way,

or you could write MMMIM
which is not standard but is

totally legal and much shorter.

Yet another issue with
Roman numerals

is that there is no zero.

Instead,

if you needed a zero,
you had to use the Latin word nulla.

Eventually, someone decided
Roman numerals needed a

numeral for zero and decided
to use N in the place of zero.

This was to represent the “n” at
the beginning of nulla.

However, the N was never really
standardized into Roman numerals

possibly because N was also
occasionally used to represent 90.

Despite all these issues however,
there are features in Roman numerals

that you probably didn't know.

For example,

fractions.

If you wanted to write ½ in Roman numerals,
you'd simply have to write an S.

Although, S technically isn't ½
but is instead 6/12.

This is because when keeping
the same base number

it's much easier to handle fractions,
such as ? and ¼,

with 12 instead of 10.

While one third of 12 is simply 4,
one third of 10 is 3 point…

yeah never mind.

While S is the base fraction,
fractions below ½ or 6/12 were still used.

Any common fractions below ½ were dots.

So 1/12 was one dot,

2/12 was two dots,

3/12 was 3 dots,

4/12 was 4 dots, and

5/12 was 5 dots.

Then beyond was of course 6/12 as S,

7/12 as S dot,

8/12 as S two dots,

9/12 as S three dots,

10/12 as S four dots,

11/12 as S five dots,

and 12/12 as I,
because of course 12/12 is just 1.

These fractions can also be
combined with other numbers.

So for example,
4½ would be written as IVS.

There are also some other
extensions to Roman numerals.

The most popular being vinculum.

Vinculum allows for much larger
numbers than standard Roman numerals.

For example the only way to write
10 thousand in standard Roman numerals

would be MMMMMMMMMM.

But this is obviously not very ideal as
it's very long and quite confusing.

Using vinculum however,

you can write 10 thousand as
X with a horizontal line over it

which multiplies X by 1000.

Or you could write it as M between
two vertical lines which multiplies M by 10.

Both are equal to 10 thousand
and both have been used.

Vinculum is the most commonly
used extension today

but there is one more that
was previously very popular.

Apostrophus was also used quite often.

If you were to write 10 thousand
using apostrophus,

you'd simply have to write
two sets of two C's,

one being mirrored,
with an I in between them.
Each additional set of C's
raises the value by a factor of 10.

Though no one ever really wrote
anything above 100,000.

It was also possible to write numbers
such as 5000 by using

I and two backwards C's.
500 was just one backwards C,

which is most likely where we get
the modern D in standard Roman numerals.

There were also some variations
of this which linked the

C's and I together like this.

Although Arabic numerals have
become the worldwide standard,

Roman numerals are still used quite often,

like as a more interesting way of displaying
a number such as the current year,

or as an additional
numbered indention in a list.

But for everyday use
and mathematics,

Arabic numerals are far superior.