Roman numerals

The system of Roman numerals is a numeral system originating in ancient Rome, and was adapted from Etruscan numerals. The system used in antiquity was slightly modified in the Middle Ages to produce the system we use today.

IIII or IV?

The notation of Roman numerals has varied through the centuries. Originally, it was common to use IIII to represent "four", because IV represented the god Jove (and later YHWH). The subtractive notation (which uses IV instead of IIII) has become universally used only in modern times. For example, Forme of Cury, a manuscript from 1390, uses IX for "nine", but IIII for "four". Another document in the same manuscript, from 1381, uses IV and IX. A third document in the same manuscript uses both IIII and IV, and IX. Constructions such as IIX for "eight" have also been discovered. In many cases, there seems to have been a certain reluctance in the use of the less intuitive subtractive notation. Its use increased the complexity of performing Roman arithmetic, without conveying the benefits of a full positional notation system.

Related Topics:
Jove - YHWH - Subtractive notation - Forme of Cury - 1390 - 1381 - Roman arithmetic - Positional notation

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Calendars and clocks

Clock faces that are labelled using Roman numerals conventionally show IIII for 4 o'clock and IX for 9 o'clock, using the subtractive principle in one case and not in the other. There are several suggested explanations for this:

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• The four-character form IIII creates a visual symmetry with the VIII on the other side, which IV would not.
• IIII was the preferred way for the ancient Romans to write 4, since they to a large extent avoided subtraction.
• It has been suggested that since IV is the first two letters of IVPITER, the main god of the Romans, it was not appropriate to use.
• The number of symbols on the clock totals twenty Is, four Vs, and four Xs; so clock makers need only a single mold with five I's, a V, and an X in order to make the correct number of numerals for the clocks. The alternative uses seventeen Is, five Vs, and four Xs, possibly requiring several different molds.
• The I symbol would be the only symbol in the first 4 hours of the clock, the V symbol would only appear in the next 4 hours, and the X symbol only in the last 4 hours. This would add to the clock's radial symmetry.
• IV is difficult to read upside down and on an angle, particularly at that location on the clock.
• Louis XIV, king of France, preferred IIII over IV, ordered his clockmakers to produce clocks with IIII and not IV, and thus it has remained.
• Clocks originally did not have hands, they only chimed the hour. There was a different chime tone for I, V and X. By having four IIII's, the wooden cog wheel could made without an additional clog and be more economical.