What's the deal with Roman Numerals?

Today's question comes to us via the medium of electronic communication, beaten on the feral drums of the caustic interface known as the internet, from a Mr Yarde of Wigan, a town famous for its pier, its pies and umm... rugby, I think?

Anyway. Mr Yarde wants to know what the deal with Roman numerals is, a question that is so cryptic that it warrants further communication, whereupon it was revealed that the questioner ponders why the tombstone above, that of one Marcus Caelius, a First Centurion of the 18th Legion has the number of said Legion depicted as XIIX and not the more familiar XVIII.

Good question. The answer is 'Because he wanted to', we must assume.

There may be a way of writing Roman numerals that you were taught in school, but in the ancient world, things weren't quite so clear-cut. There never was and never has been any accepted standard for how Roman numerals are expressed.

In simple terms, Roman numerals use a combination of Latin alphabet letters allied to a tally system. Like all tally systems, it's simply a matter of counting how many strokes are made to read the number expressed. You can count how long a prisoner has been in a jail cell, should you ever be arrested, by counting the strokes carved into a wall, and you can count in Roman numerals in the same way, too.

Roman numerals use an additive form, where another tally is added to the previous one to form a new number: I, II, III, IIII and so on. Various letters are then used to signify powers of 5 and 10: V, X, L, C, D and M.

A subtractive system can also be used where a tally is subtracted from the larger number for no other reason than it looks quite nice: IV, IX, XC, CD and so on.

So, which one did the Romans use?

All of them. Any of them. Sometimes, all at once. And the beauty and simplicity of the system is that as long as you understand the basics, you can read the numbers no matter how you use them. So, 'IIX' might upset some people because they expect to see 'VIII', but not only is it perfectly acceptable, but the Romans themselves used IIX to mean 8, as we can clearly see from the tombstone.

His tombstone reads:

M[ARCO] CAELIO T[ITI] F[ILIO] LEM[ONIA TRIBV] BON[ONIA]

P[RIMVS] O[RDO] LEG[IONIS] XIIX ANN[ORVM] LIII S[EMISSIS]

[CE]CIDIT BELLO VARIANO OSSA

[HVC] INFERRE LICEBIT P[UBLIVS] CAELIVS T[ITI] F[ILIVS]

LEM[ONIA TRIBV] FRATER FECIT

In English:

"To Marcus Caelius, son of Titus, of the Lemonian district, from Bologna

First Centurion of the Eighteenth Legion, 53 and a half years old.

He fell in the Varian War

His freedman's bones may be interred here. Publius Caelius, son of Titus,

of the Lemonian district, his brother, erected [this]"


It might suggest that the 18th Legion preferred to use this form of notation for their name or that such a system was all the rage in the fashionable part of the early 1st century AD. However, if we look at the funerary inscription for another soldier of the 18th Legion, Gaius Pompeius Proculus, we see something different:

This one reads:

C[AIUS] POMPEIVS C[AIUS] F[ILIO] TER[TIUS]
PROCVLVS
TRIB[UNUS] MIL[ILITUM] LEG[IO] XVIII
PRAEFECTVS FABRUM
SEVIR CENTVR[IAE] EQUIT[ES]
HIC SEPVLTVS EST

In English:

”To Gaius Pompeius Proculus, third son of Gaius,
Military Tribune of the Eighteenth Legion,
Praefectus Fabrum [a prefect in charge of craftsmen]
Sevir [an honorary title] of the Equestrian Units
Is Buried Here”

The 18th Legion is destroyed in the Varian disaster of AD 9 alongside the 17th and the 19th and those numbers are never used for legions again. So, these two were serving in the same legion, at the same time, yet they are both using different numbering notations.

It really is just a matter of personal choice, it seems.

Elsewhere, we see the seemingly haphazard approach applied to architecture. Around the outside of the Colosseum are a series of numbered entry gates. Here is Number 52, LII, as you’d expect:

And here is Number 54. Rather than the expected LIV, they have used LIIII. Two different numbering systems on the same building, presumably built by two different labouring gangs or masons, who were either told to do it this way or to number the gates and left to get on with it.

The truth is that there is no defined way of expressing Roman numerals. Even the Romans themselves didn’t have one, as the epigraphical record demonstrates.

Like most forms of communication, the important thing is getting one’s message across and as long as one can be understood by the recipient of the message, feel free to use whatever system you like.

The Romans did.




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