数字とローマ数字を相互変換
Numbers above 3,999 use vinculum notation: a line above a numeral multiplies its value by 1,000.
So XCCCXX = 10,320.
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Did you know?
No Zero, No Problem
Roman numerals have no symbol for zero. The concept of zero didn't reach Europe until centuries after the fall of Rome, arriving via Indian mathematicians and Arab traders. The Romans didn't need zero for their purposes — you can't owe zero taxes or march zero soldiers. It's only when you need placeholder arithmetic (like 101 vs 11) that zero becomes essential.
Read more →Why Movies Use Roman Numerals in Credits
Look at the end credits of almost any film and you'll see the year in Roman numerals: MMXXVI instead of 2026. This tradition started as a way to make the copyright year less obvious — studios didn't want audiences to know immediately how old a film was during reruns. The practice stuck, and now it's just how it's done.
Read more →ローマ数字はどこから来たのか？
ローマ数字は手の合図や数え棒に由来すると考えられています。線のIは指1本を、Vは5を表す親指と指の間の隙間を、Xは10を表す交差した両手を表しています。L、C、D、Mはギリシャ文字のカイ、シータ、ファイを変形させたもので、それぞれ50、100、500、1,000を表します。時が経つにつれ、これらの記号は今日知られているラテン文字へと変化しました。ローマのアルファベットには0がありません。0の概念は、インドが紀元600年頃 / 10600 HEに発明するまで完全には発達しなかったためです。