As we explored in the previous segment, there is nothing inherent to Japanese phonology itself that accounts for the large number of homophones. Given the language’s inventory of phonemes and phonotactics, it is more than capable of coming up with enough unique words to avoid homophones altogether.
So why are there still so many homophones? The first reason is simply the fact that not all mora combinations are actually used. For example, the string of sounds むりゃこ、ばじゃわま、ちゃびゅうしゃん and ぱんぎん are all valid sequences in Japanese, but they simply do not show up in the standard lexicon as real words. These are called accidental gaps and Japanese is full of them. We have accidental gaps in English too. For example, the made up words plarg, beetazoom and lummy are all valid constructions according to the rules of English phonology, but they do not mean anything.
Although accidental gaps account for a part of the problem, they are not the main cause. That dubious honor goes to on-yomi, which, as you might remember from a previous post, are Chinese morphemes borrowed into Japanese. The Chinese languages (which from here on out I will just refer to as Chinese for simplicity) are much more phonologically rich languages than Japanese.
First, all varieties of Chinese are tonal, meaning that the pitch contour of each syllable is lexically significant. Tones are used to distinguish words in same way as consonants and vowels. Mandarin has 4 tones while Cantonese has 6-9 tones, depending on who you ask. Japanese on the other hand is not tonal. This means that words that would have been distinguishable by tone alone in Chinese became homophonous when borrowed into Japanese. For example, the Chinese words mā, má, mǎ, and mà, which all have different tones and are thus distinct in Chinese, all become simply ma in Japanese.
Additionally, Chinese phonotactics are more complex than Japanese. For example, Chinese allows the sounds and to appear in a syllable coda whereas Japanese only allows one sound, ん・ン, which sounds close to . So Chinese bang and ban simply become ばん (ban) in Japanese.
Lastly, on-yomi are all very short. Morphemes in Chinese are generally monosyllabic (although words can be made up of multiple morphemes and thus be polysyllabic). As a result, monosyllabic Chinese morphemes were borrowed into Japanese as one or two mora morphemes like こう、しん、りゃく, etc. This doesn’t leave much room for variety. In fact, there are only about 300 or so on-yomi in use in the modern language.
On the other hand, Kun-yomi can be very long. Some rather long kun-yomi include はたらく、うけたまわる and こころざし. This tendency of kun-yomi to be longer means that there are more possible sound combinations to work with, resulting in fewer overall homophones.
The end result of all this is that dozens of morphemes that were all distinct in Chinese all got mapped to the same sounds in Japanese. Take a look at the chart below.
This chart shows 46 different words, all of which are distinct in Mandarin and homophonous in modern Japanese. They are mostly distinct in Cantonese and Korean as well, with only a couple exceptions.
What is fascinating though is the difference between old Japanese and modern Japanese. In old Japanese we see a fair amount of diversity in pronunciation, albeit far less than in Korean. Not only that, but all of these pronunciations in old Japanese, with the exception of くゎうしゃう and くゎうしょう are still possible in the modern language.
This means that modern Japanese has homophones where it doesn’t even need to have homophones. Why not simply use the pronunciations かうしゃう、かふしゃう or こうせう like back in the Nara period?
The simple and emotionally unsatisfactory answer most of the time is that phonological drift is something that just happens, for better or worse. It is something that all languages are in theory subjected to. From this perspective, there is no grand overarching reason that all of the pronunciations of old Japanese changed to こうしょう.
However, in the case of Japanese, it is possible to pinpoint a few key elements of Japanese society that arguably contributed to the rise in homophones. I will be discussing what these elements were in the next installment.