What are Roman Numerals?
Roman Numerals are a numeral system for writing numbers, originally used by the ancient Romans.
The Romans may have been the first people to use letters to represent numbers, but it is uncertain how they came to be. They are mentioned in Latin literature, but only as an alternative to other numerical systems. The earliest known written numerals are the Vrune and the Crune on a bone plate found in Denmark. Other early numerals include examples of inscribed tally
In history, there have been many different types of writing systems that were used in various parts of the world. One such system is the Roman numerals that have been in use since ancient times.
How to Write a Multilingual Letter or Email using the Roman Alphabet
One of the most common ways to write in English is by using the Roman Alphabet. It can be used for both grammar and spelling.
The following are the rules to write in English using the Roman Alphabet:

Use lower case letters ($A, $B, $C) for all words that start with a consonant sound ($a, $b, $c).

Do not use capital letters when writing acronyms or acronyms themselves.

Do not use a comma after coordinating conjunction such as “and,” “or,” or “but.”

When writing a question mark (“What did you eat today?”), but it at the end of your sentence if it’s just one word long and only if you’re talking about
The History of Writing in English and How it has Improved with the Use of Roman Numerals
Writing in English started when the Romans came to Britain. The Romans came with a system of writing called Roman Numeral. They used this system to write down their language and the problems they encountered when trying to learn it became huge.
The use of Roman Numerals in England was not an easy process because it was difficult for them to pronounce and remember how many letters and symbols there were and how they worked together. Fortunately, John Dunbar simplified their use by creating alphabetical order of characters that made it easier for people to learn and read.
With the increase in literacy, more people became able to share ideas which led to improved writing skills overall.
Roman Numerals in Modern English Writing and Why They Were Chosen Over Other Alphabets
The roman numerals in English writing are used for numbers from one to four, five through nine, and one thousand. In addition to spelling out the numbers, they also serve as a mnemonic device for learning how to count in English.
The Romans chose to use roman numerals because it was much easier for them when writing down numbers from one through four. They quickly adopted the system when they began writing about higher number values.
The Romans were able to use the same system of digits that they were familiar with just a different way in which they read them. The roman numerals have remained popular because it is easier for people to read and write them then other systems such as Arabic or Hebrew
The Secret History of Writing in English and Why It Wasn’t Used for Centuries Before Using Roman Numerals
The story of how the English language developed is quite interesting. But, it’s also quite complicated.
Many of the earliest words in the English language come from Scandinavian languages like Danish, Norwegian, and Swedish. The English language was created by combining these words with AngloSaxon (Old Norse) words which had their origins in Denmark, Norway, and Sweden.
The use of Roman numerals for writing dates back to around 600 BC where it was used by ancient Greeks and Romans for writing numbers. It wasn’t until the 1300s that this practice spread to France, Italy and Spain before finally arriving in England around 1586.
The date format is in the form “MMXVII” in Europe, Asia, Africa, and most countries around the world.
Roman Numeral Conversion Tables for Common Western Languages
Roman numbers are a way to represent numbers in many languages. The system was originally developed by the Romans for their use with counting. The current order of the Roman numerals is Z, X, C, D, L, then I, V, and finally M.
How to Use Roman Numerals When Writing Math Equations
When it comes to writing math equations, most people either use decimal numbers or fractions. However, a simple change in a math equation can make it easier to read and understand.
The key is to use the roman numerals in place of decimal numbers when writing equations or when translating from an equation written in another language.
In the example below, the equivalent decimal number is 889. The equation can be written out as IV=V+1/4 which is one of the simplest ways to write an equation with roman numerals.
Bold Roman Numerals with Numbers for Beginning of Year or End of Year
Bold Roman numerals are a type of typographic ornamentation used to emphasize the start or finish of a year. They are mostly used in annual publications like calendars. An example of this is seen with the number 1 representing the first year of the 21st century.
The boldfaced roman numerals with numbers for the beginning of year or end of the year are often used in annual publications like calendars. An example is seen with the number 1 representing the first year of the 21st century.
Roman numerals – by Wikipedia
Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe until the late Middle Ages. Numbers in this system are represented by combinations of letters from the Latin alphabet. Modern usage employs seven symbols, each with a fixed integer value:
Symbol  I  V  X  L  C  D  M 

Value  1  5  10  50  100  500  1000 
The use of Roman numerals continued long after the decline of the Roman Empire. From the 14th century on, Roman numerals began to be replaced by Arabic numerals; however, this process was gradual, and the use of Roman numerals persists in some applications to this day.
One place they are often seen is on clock faces. For instance, on the clock of Big Ben, the hours from 1 to 12 are written as:
I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII
The notations IV and IX can be read as “one less than five” and “one less than ten”. There is a tradition favoring the representation of “4” as “IIII” on Roman numeral clocks.
Other common uses include year numbers on monuments and buildings and copyright dates on the title screens of movies and television programs. MCM, signifying “a thousand, and a hundred less than another thousand”, means 1912, so 1912 is written MCMXII. For the years of this century, MM indicates 2000. The current year is MMXXI (2021).
Standard form
The following table displays how Roman numerals are usually written:
Thousands  Hundreds  Tens  Units  

1  M  C  X  I 
2  MM  CC  XX  II 
3  MMM  CCC  XXX  III 
4  CD  XL  IV  
5  D  L  V  
6  DC  LX  VI  
7  DCC  LXX  VII  
8  DCCC  LXXX  VIII  
9  CM  XC  IX 
The numerals for 4 (IV) and 9 (IX) are written using “subtractive notation”,[6] where the first symbol (I) is subtracted from the larger one (V, or X), thus avoiding the clumsier (IIII, and VIIII).[a] Subtractive notation is also used for 40 (XL) and 90 (XC), as well as 400 (CD) and 900 (CM).[7] These are the only subtractive forms in standard use.
A number containing several decimal digits is built by appending the Roman numeral equivalent for each, from highest to lowest, as in the following examples:

39 = XXX + IX = XXXIX.

246 = CC + XL + VI = CCXLVI.

789 = DCC + LXXX + IX = DCCLXXXIX.

2,421 = MM + CD + XX + I = MMCDXXI.
Any missing place (represented by a zero in the placevalue equivalent) is omitted, as in Latin (and English) speech:

160 = C + LX = CLX

207 = CC + VII = CCVII

1,009 = M + IX = MIX

1,066 = M + LX + VI = MLXVI
Roman numerals for large numbers are seen in the form of year numbers, as in these examples:

1776 = M + DCC + LXX + VI = MDCCLXXVI (the date written on the book held by the Statue of Liberty).

1918 = M + CM + X + VIII = MCMXVIII (the first year of the Spanish flu pandemic)

1954 = M + CM + L + IV = MCMLIV (as in the trailer for the movie The Last Time I Saw Paris)

2014 = MM + X + IV = MMXIV (the year of the games of the XXII (22nd) Olympic Winter Games (in Sochi, Russia))
The largest number that can be represented in this notation is 3,999 (MMMCMXCIX), but since the largest Roman numeral likely to be required today is MMXXI (the current year) there is no practical need for larger Roman numerals. Prior to the introduction of Arabic numerals in the West, ancient and medieval users of the system used various means to write larger numbers; see Large numbers below.
Source: Wikipedia