rendaku

is a pronunciation change seen in some compound words in Japanese. Rendaku modifies the consonant at the start of the second (or later) part of the compound, replacing a voiceless consonant, such as , with a voiced consonant, such as . For example, the morpheme starts with the voiceless consonant , which is replaced with the corresponding voiced consonant in the compound word , from + .

Rendaku is common, but it does not occur in all compound words. A rule known as Lyman's law blocks rendaku when the second element already contains one of the voiced obstruent phonemes , as in the compound word . Because the second element contains , its initial consonant remains voiceless. Rendaku is also blocked almost always when the second element of a compound is a recent loan into Japanese. Furthermore, rendaku may fail to occur even in contexts where no definite blocking factor is present.