“You’ve been in Japan too long when you can do arithmetic in oku, cho and kei.” My father-in-law loves to sit around in our rural liquor shop reading the paper as he waits for customers to come in, though he’s usually waiting a long time since most of our customers are in their 70s, and keep dying. The other day I happened to pick up a newspaper he’d been reading and noticed that the new budget for Japan’s fiscal year had been announced, at 92 cho yen. This number was quite meaningless to me, not only because it was very large and in yen, but also because it was expressed in the kanji-based number system used in China and Japan. While the Arabic number system is based on units of 1,000, the Sino-Japanese numeric system uses 10,000 (man, pronounced “mahn”) as its main unit. Instead of writing 10,000, you write ichi mahn or 1-10,000, and to express 3 million you’d write 300 mahn or 100 units of 10,000. These numbers aren’t too bad, since they’re used in everyday life, but for very high numbers, which use seldom-seen kanji like oku (100 million), cho (1 trillion) and kei (10 quadrillion), my brain shuts down pretty quickly…
