numbers: Roman numerals

Roman numerals are becoming increasingly rare, but they still have the following uses:

• names of rulers, aristocrats, and the names of ships, racing cars and space vehicles:
  • Charles IV
  • Pius XII
  • Bluenose II
  • Saturn V
• numbers of volumes, chapters, tables, plates, acts and other divisions of a book or play (now often replaced with Arabic numerals):
  • Psalm XXIII
  • Volume XII
  • Appendix III
  • Act II, Scene iii (act number in upper case, scene number in lower case) Iliad xi.26
• Government of Canada Statutes:
  • Schedule IV
  • Part III
• years, centuries and recurring events of major importance:
  • MCMLXIV (in very formal contexts)
  • XIX century (or 19th century)
  • XXIII Olympiad

Do not use ordinal forms (st, nd, th, etc.) with Roman numerals.

Lower-case Roman numerals may be used for page numbers in preliminary matter (preface, foreword, table of contents, etc.), subclauses and subordinate classifications in a series.

• page xi of the Preface

Note that a bar over a letter in a Roman numeral multiplies its value by 1000:

• _
  D = 500 000
• _
  V = 5000

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