\begin{definition}[Definition:Roman Numerals]
The '''Roman numerals''' are:
{{begin-eqn}}
{{eqn | l = \mathrm I:
      | o = \)'''unus'''\(:
      | r = 1
}}
{{eqn | l = \mathrm V:
      | o = \)'''quinque'''\(:
      | r = 5
}}
{{eqn | l = \mathrm X:
      | o = \)'''decem'''\(:
      | r = 10
}}
{{eqn | l = \mathrm L:
      | o = \)'''quinquaginta'''\(:
      | r = 50
}}
{{eqn | l = \mathrm C:
      | o = \)'''centum'''\(:
      | r = 100
}}
{{eqn | l = \mathrm D:
      | o = \)'''quingenti'''\(:
      | r = 500
}}
{{eqn | l = \mathrm M:
      | o = \)'''mille'''\(:
      | r = 1000
}}
{{end-eqn}}
To express other numbers than these, symbols are placed next to each other so as to cumulate: for example:
:'''$\text {II}$''' means $2$
:'''$\text {CCXVI}$''' means $216$.
For brevity in presentation, the technique is used of placing a smaller denomination in front of a larger one so as to subtract the former from the latter
For example:
:'''$\text {IV}$''' means $4$
:'''$\text {XCIX}$''' means $99$ (although '''$\text {IC}$''' could be used, it is not).
Arithmetic using '''Roman numerals''' is cumbersome and pointless, although some sadistic and worthless grade-school arithmetic texts insist on setting such operations as exercises.
For doing arithmetic, abacism was the usual technique, originating in ancient times. It is still used in rural areas of, for example, the Asian steppes, where writing materials are not to be wasted and electronic aids are un-needed.
With the invention of the techniques offered by the so-called Arabic numerals in mediaeval times, an alternative method of doing arithmetic developed, called algorism.
\end{definition}