Rendaku (連濁^?, lit. "sequential voicing") is a phenomenon in Japanese morphophonology that governs the voicing of the initial consonant of the non-initial portion of a compound or prefixed word. In modern Japanese, Rendaku is common but unpredictable.^{[citation needed]}

Rendaku can be seen in the following:

In some cases, rendaku varies depending on syntax. For instance, the suffix 〜通り ("road, following"), from 通る tōru "to go, to follow", is pronounced as 〜とおり -tōri following the perfective verb tense, as in 思った通り omotta-tōri "as I thought", but is pronounced as 〜どおり -dōri (with rendaku) when following a noun, as in 予定通り yotei-dōri "as planned, according to schedule" (or, semantically differently – more concretely – 室町通 Muromachi-dōri, "Muromachi Street").

Research into defining the range of situations affected by rendaku has largely been limited to finding circumstances which cause the phenomenon not to manifest itself:

Lyman's Law states that rendaku does not occur if the second consonant of the second element is a voiced obstruent, a consonant sound formed by obstructing airflow. This was later modified to state that rendaku does not occur when the second element of the compound contains a voiced obstruent in any position (see third example below). This is considered to be one of the most fundamental of the rules governing rendaku.

Tadashi Mori (森 正, Mori Tadashi^?, 14 December 1921—4 May 1987) was a Japanese conductor and flautist.