To be fair, zero is a complicated number
9 points
We do know why, it’s because death 死 and four 四 have the same pronunciation sǐ in Chinese (and shi in Japanese).
5 points
2 points
homophones are common in Chinese and Japanese because there’s only so many potential readings of a hieroglyph, but each one has a different meaning
1 point
Sure, but they’re often different enough to to be obvious in context, or similar enough to have a shared etymology.
Tones came later in Chinese, so when you have 2 homophones with similar meaning and different tones, they’re usually from words that had 2 suffixes, which were later dropped, but the tone of first part remained, 买 and 卖 didn’t end up with the same word by coincidence.
