What is the significance of the character "j" at the end of a Roman Numeral? (2013)

Original Article ↗ Hacker News Discussion ↗

Use of “j” in Roman numerals (esp. in prescriptions)

  • Thread centers on the use of a final “j” (e.g., xvij) in Roman numerals, especially in historical medical prescriptions.
  • A cited 1919 instruction says numerals are written with a line above, and dots of i and j placed above that line; the final i is written as j.
  • The “j” functions as a visual terminator: it marks the end of the sequence of ones and is part of the number (xvij = 17, not 16).

Forgery vs. error prevention

  • One view: the “j” and overline made it harder to alter ii to iii, or to append extra digits, similar in spirit to anti-fraud measures on checks.
  • Counterpoints:
    • It remains easy to alter other symbols (e.g., X → XX), or to extend the overline.
    • The cited historical text appears more concerned with preventing misreading and mistakes than with deliberate fraud.
  • Consensus in the thread leans toward “making tampering more difficult and errors less likely,” not making it impossible.

Comparison to checks and legal documents

  • Analogies drawn to writing numbers twice (digits and words) on checks and contracts to reduce ambiguity and tampering.
  • Mention of “termination” words like “dollars only” and horizontal strokes to block extra additions.

Historical letterforms and ligatures (i/j, u/v, etc.)

  • Multiple comments note that i and j, and u and v, were historically variants of the same letters; distinctions solidified later.
  • Long-s in English and its evolution to ß in German are discussed as parallel typographic conventions.
  • Similar “final” forms exist in Hebrew and Greek letters.

Dutch “ij” and related digraphs

  • The Dutch digraph ij is linked to the same tradition: originally ii, then ij, with the last i elongated.
  • It’s treated partly as a single letter, can be written like ÿ in cursive, and its pronunciation and teaching in schools are discussed in depth.
  • Pronunciation of “Dijkstra” and the Dutch diphthong /ɛi/ vs English diphthongs is debated.

Skepticism and AI sourcing

  • Some point out that modern explanations citing anti-forgery may be oversimplified or misread from sources.
  • There is explicit criticism of answers that appear to be copied from language models without checking the original historical references.