Rendaku occurs most frequently in compounds where the second element is a single morpheme of
native Japanese origin that does not already contain a voiced obstruent phoneme. However, even though rendaku is usual in this context, it does not invariably occur: there are numerous exceptions pronounced without rendaku. Some compound words are pronounced with rendaku by some speakers, but without it by other speakers. Rendaku is blocked when a voiced obstruent phoneme is already present in the second element of the compound. This rule, called Lyman's law, is highly reliable, with only a small number of exceptions. Rendaku is also blocked if the second element is a recent loanword from a language other than Chinese (
gairaigo). This rule likewise has few exceptions. Rendaku does not affect most
Sino-Japanese elements, but this tendency is less consistent. A substantial minority do undergo rendaku as the second element of a compound. It has been speculated that Sino-Japanese elements that can undergo rendaku might have become "vulgarized", that is, adopted into the same category of vocabulary as native Japanese morphemes. Other rules have been proposed regarding circumstances where rendaku is either blocked or favored, but often, it is only possible to identify tendencies rather than inviolable rules.
Lyman's law '''Lyman's law''' is a fundamental constraint on rendaku that prohibits voicing when the second element of a compound already contains a voiced obstruent phoneme (, , , or , including
allophones such as and ). These phonemes are all written with the
dakuten and called in Japanese. For example: • + → (surname) ("mountain" + "gate" → place name). Rendaku does not occur because already contains a voiced obstruent consonant phoneme . Therefore, its initial consonant remains voiceless, and the form *
Yamagado やまがど does not exist (* indicates a non-existent form). • + → ("one person" + "travel" → "traveling alone"), not *. Rendaku does not occur because already contains a voiced obstruent consonant phoneme . • + → ("mountain" + "fire" → "mountain fire"), not *. Rendaku does not occur because already contains a voiced obstruent consonant phoneme (in the form of its allophone ). The precise formulation of Lyman's law varies between analysts. In particular, there are conflicting viewpoints on the size of the phonological domain in which it applies. One formulation states that
rendaku is blocked by the presence of a voiced obstruent consonant "within a morpheme"; this may be interpreted as a consequence of a more general constraint that applies also to the underived form of native Japanese morphemes, which do not generally contain more than one voiced obstruent phoneme. An alternative view is that Lyman's law applies whenever a voiced obstruent consonant occurs anywhere within the second element of a compound, and so might also include cases where this element is composed of more than one morpheme. Rendaku occasionally (although relatively infrequently) causes voicing of the initial consonant of a
Sino-Japanese () lexeme that is written with two kanji, and is in etymological terms composed of two Sino-Japanese roots; it is debatable whether such lexemes count as one morpheme or two from a
synchronic perspective. In modern Japanese, the presence of a voiced obstruent phoneme in the first element does not normally block rendaku, as demonstrated by examples such as + → . Nevertheless, it has been proposed that in certain circumstances, Lyman's law might be (or might once have been) sensitive to the presence of a voiced obstruent in the first element of a compound. Compound personal names ending in the element 'rice field' seem to usually show rendaku when the final mora of the first element contains (e.g. ), but never show rendaku when the final mora of the first element contains (e.g. ) (and usually do not show rendaku when it contains ). The pattern of voicing seen in compounds like these may in part be a residue of an older version of the law that operated in Old Japanese. Examination of Old Japanese compounds suggests that Old Japanese had a constraint against two consecutive syllables starting with a
prenasalized consonant (the source of modern Japanese /voiced obstruent phonemes), but over time, this constraint came to be replaced with the modern tendency for a consonant to block rendaku only when it occurs in the second element of the compound. Some formulations of the law state that rendaku is blocked in cases where a /voiced obstruent phoneme is the second consonant in the non-initial element of the compound. However, in modern Japanese, there is evidence that Lyman's law generally also applies to morphemes containing a consonant in their third or later syllable. This is indicated by the lack of rendaku in examples such as + → or + → . There are only a handful of exceptions, such as + → , where voicing occurs despite the presence of a /voiced obstruent consonant in the second element of the compound. In the case of Old Japanese, there is not enough evidence to conclude whether the Old Japanese version of Lyman's law applied to morphemes containing a prenasalized consonant in their third or later syllable. Although this law is named after
Benjamin Smith Lyman, who independently propounded it in 1894, it is really a re-discovery. The
Edo period linguists
Kamo no Mabuchi (1765) and
Motoori Norinaga (1767–1798) separately and independently identified the law during the 18th century.
Source language of the second element Another important factor affecting the likelihood of rendaku is the etymological source or
lexical stratum of the second element of the compound. Rendaku frequently affects
wago (native Japanese lexemes), infrequently affects
kango (Sino-Japanese vocabulary), and very rarely affects
gairaigo (recent loanwords, such as borrowings from English). On the other hand, the lexical stratum of the first element of the compound is not relevant. One possible reason for the resistance of Sino-Japanese morphemes to rendaku is the greater potential for it to cause homophony in this context. Native Japanese morphemes very rarely start with a voiced obstruent consonant, but this does not apply to Sino-Japanese; therefore, rendaku of Sino-Japanese morphemes is more likely to neutralize a contrast between distinct morphemes.
Kango Sino-Japanese vocabulary is built from Sino-Japanese roots, which have a restricted phonological structure (one or two moras long). At least half of Sino-Japanese terms are "binoms" consisting of two roots, but some roots can be used on their own as words (mononoms). A binom is written with two
kanji (Chinese characters), one for each root. Most Sino-Japanese lexemes do not undergo rendaku when used as the second element of a compound. However, a minority (around 20% of mononoms, and 10% of binoms) do show rendaku in at least some compounds. No criteria have been identified that predict with 100% accuracy when this occurs. In terms of phonology, rendaku is blocked by Lyman's law and so never affects a binom where the second root starts with a voiced obstruent phoneme; e.g. in , in . Based on a study of how native speakers pronounced novel compounds, concluded that rendaku is statistically less likely to affect a Sino-Japanese binom where the first root ends in the moraic nasal and the second root end in a voiceless obstruent, although it is not fully blocked in this context (the study's observed rate of rendaku in this context was 1.3%, compared to Vance 1996's dictionary-based estimate of rendaku affecting 10% of all Sino-Japanese binoms). Sino-Japanese roots that start with voiceless obstruents may have variant pronunciations starting with voiced obstruent phonemes for other reasons aside from rendaku. One reason is the existence of different readings of Sino-Japanese roots, corresponding in general to different time periods of borrowing. Two of the most important types of reading are termed Go-on and Kan-on. Some (though not all) Kan-on readings starting with
correspond regularly to Go-on readings starting with : these represent different adaptations of Early Middle Chinese voiced obstruent sounds, and so the existence of these alternative pronunciations is unrelated in origin to rendaku. An example is the root 'ground, land', which has both a Kan-on pronunciation and a Go-on pronunciation . For this reason, the use of the voiced pronunciation in compounds such as cannot necessarily be attributed to rendaku, since the version of this root can also be found at the start of a word, e.g. in . In addition, a minority of lexemes composed of two Sino-Japanese roots display a type of sequential voicing, affecting only roots in second position, that is indistinguishable in effect from rendaku, but probably has a distinct origin in terms of morphology. The relevant context is forms such as , which appears to display rendaku on its second element . In this case, voicing is hypothesized to be the result of the preceding Sino-Japanese root originally ending in a nasal sound, which caused the following consonant to become prenasalized and voiced. Prenasalization and voicing of a consonant after a nasal sound () is hypothesized to have been an active phonological rule up through
Early Middle Japanese; in
Late Middle Japanese, were denasalized and voicing after ceased to be automatic.
Gairaigo Gairaigo vocabulary is usually not affected by rendaku when it occurs as the second element of a compound, as illustrated by the contrast between 'glass shelf', from native Japanese 'shelf', and 'glass case', from foreign 'case': rendaku does not occur and is not expected to occur in the latter compound word, since its non-initial element belongings to foreign vocabulary. (In contrast, as shown by , the use of a
gairaigo word as the first element of a compound does not prevent rendaku of a following native element.) Examples where rendaku affects a
gairaigo element of a compound are highly exceptional.
Part of speech Rendaku affects compounds involving various parts of speech, such as Noun + Verb, Adjective + Noun, Verb + Noun, Verb + Adjective; however, it is rare in compounds of the form Verb + Verb.
Reduplication Rendaku is very frequent in words formed by
reduplication, other than
mimetic words, which are immune to rendaku. Examples: : (
iteration) ::
hito +
hito →
hitobito ("person" + "person" → "people") : (iteration) ::
toki +
toki →
tokidoki ("time" + "time" → "sometimes")
Semantics Rendaku tends not to occur in non-reduplicative compounds which have the
semantic value of "X and Y" (so-called
dvandva or copulative compounds), as exemplified by
yama +
kawa >
yamakawa "mountains and rivers", as opposed to
yama +
kawa >
yamagawa "mountain river".
Branching compounds In compounds containing more than two elements (or compounds where one element is itself a compound), the
branching structure of the compound may affect the application of rendaku. For example, , a compound of the morphemes "door" and "shelf", retains its initial voiceless when used as the second element of the compound "small cupboard". In examples like this, where the second element contains a voiced consonant as a result of rendaku, the lack of voicing at the start of the second element of the larger compound can potentially be explained as a consequence of
Lyman's law. proposed that rendaku is blocked in general in the left-branching elements of a
right-branching compound, even in cases where Lyman's law does not apply. However, other linguists have questioned the validity or necessity of formulating such a constraint. The branching constraint is intended to explain the contrasting behavior of examples such as the following: :
mon + [
shiro +
chō] >
monshirochō, not *
monjirochō ("
family crest" + ["white" + "butterfly"] > "
cabbage butterfly") but :[
o +
shiro] +
washi >
ojirowashi (["tail" + "white"] + "eagle" > "
white-tailed eagle") This constraint does not apply to all words where the second element is composed of more than one morpheme. As discussed above, rendaku can affect Sino-Japanese "binoms" composed of two Sino-Japanese roots. Assuming the branching constraint is valid, it is possible it does not prevent rendaku in that context because Sino-Japanese binoms do not have the morphological status of compound words in the context of rendaku. In any case, there seem to be some counterexamples to the branching constraint, such as 'big talk', from 'big' + , from ' bath' + 'carpet', or 'fire brigade for common people', from 'town' + , from 'fire' + 'to extinguish'. Other examples where rendaku appears to affect "multi-root" elements that are themselves composed of smaller elements (at least in terms of etymology) include the following: • () 'tavern', from 'staying' + 'saké-shop', from 'saké-' + '-shop' • () 'socializing with people', from 'person' + ()'socializing', from 'attaching' + 'matching' • () 'skirmish', from 'small' + 'competition', from 'vying' + 'matching' • () 'sole (fish)', from 'tongue' + 'flounder', from 'flat' + 'eye' Otsu accounted for apparent counterexamples to the branching rule by postulating a distinction between "loose" and "strict" compounds. Per Otsu, loose compounds are formed in a productive manner, have a predictable meaning based on their components, and follow the general accentuation rules for compound words. Loose compounds are hypothesized to be immune to rendaku when used as the right-hand element of a larger compound, whereas "strict" compounds can undergo rendaku the same way as single morphemes. However, Vance 2022 argues it is not clear that these criteria can really be applied reliably to predict whether a compound is "loose" or "strict" for the purposes of rendaku. The branching constraint analysis could be considered a violation of the Atom Condition, which states that "in lexical derivations from X, only features realized on X are accessible." An alternative view proposes that the process applies cyclically. :[
nuri +
hashi] +
ire >
nuribashiire ([lacquered chopstick] case, "case for lacquered chopsticks") :
nuri + [
hashi +
ire] >
nurihashiire (lacquered [chopstick case], "lacquered case for chopsticks") This could be seen as the voicing between hashi and ire staying unrealized but still activating Lyman's law. Ito and Mester 2003 proposed a third account distinct from both Otsu 1980's branching-based constraint and Ito and Mester 1986's cyclical account. This hypothesis holds that the relationship between branching and rendaku is not direct, but is mediated by
prosodic structure: the lack of rendaku in right-branching compounds such as is analyzed as a consequence of coming at the start of a prosodic word. Per Ito and Mester 2007, whether a compound is treated as one or as multiple prosodic words is affected by the length of the second element of the compound: if the second element is longer than four moras (or two bimoraic feet), then the compound is required to have the prosody of a phrase rather than a single word.
Further considerations In some cases,
rendaku varies depending on syntax. For instance, the suffix , from , is pronounced as following the
perfective verb, as in , but is pronounced as when following a noun, as in or, semantically differently – more concretely – . Most
Japanese family names are compounds, and rendaku may or may not affect the second element of a compound name. Some names are read in different ways for different people, and have both a reading with rendaku and one without, such as (which can be either or , among other readings).
Lexical propensity It has been hypothesized that morphemes are inherently either more susceptible or more resistant to being voiced when used as the second element of a compound; in other words, that the propensity of a morpheme to undergo rendaku is lexically specified. Some morphemes show voicing in all compounds in which they occur. At the far end of the spectrum, a small percentage of morphemes appear to be immune to rendaku (for reasons not explained by the phonological, morphosyntactic, and lexical-stratum factors described above that regularly block rendaku). Other morphemes are intermediate and undergo voicing in some but not all compounds. found that out of elements that occurred at least 5 times in second position in a database of frequent compound words, the most common behavior (42%) was to undergo voicing in all compounds, and each range of greater resistance to rendaku contained successively fewer elements (35% had voicing rates from 0.667 to 0.999; 12% had voicing rates from 0.334 to 0.666; 7% had voicing rates from 0.001 to 0.333, and 5% were never voiced). suggests that the first element of compound words also has a lexically variable propensity to trigger rendaku, hypothesizing that rendaku occurs in words where the combination of these two voicing weights (the rendaku-triggering weight of the first element and the rendaku-undergoing weight of the second element) exceeds a threshold value, and fails to occur when this value falls below the threshold.
Word length In some circumstances, rendaku appears to be affected by the length of a compound word, as measured in
moras. Certain second elements that have a length of one or two moras tend to resist rendaku when combined with a first element that is one or two moras long. (A compound where both elements are short can be called a "short-short compound"). For example, occurs without rendaku in a number of short-short compounds, such as and . However, these resistant elements undergo rendaku in compounds where the first element is three or more moras long, such as .
Avoidance of bVmV Rendaku seems to be avoided in non-verbal elements that start with or + vowel + + vowel, such as , which has been explained as an effect of a preference against having
homorganic consonants at the start of adjacent syllables: rendaku would replace or with , which is bilabial like . Rendaku is seen before vowel + + vowel in 'love letter' from 'letter': this is consistent with the hypothesis, since contains , which is already homorganic with (and so avoiding rendaku would not make any difference). (An alternative explanation supposes that , as well as other words that undergo rendaku to , starts with an underlying labial consonant that is phonologically distinct from the found at the start of lexemes that do not undergo rendaku.) A study observed this tendency as an active factor affecting the frequency with which Japanese speakers preferred rendaku vs. non-rendaku variants of
nonce words. For whatever reason, this avoidance is not seen in verb roots (including deverbal nouns), which undergo rendaku even in cases such as 'to corrupt'. No comparable effect is seen with other consonant sounds that undergo rendaku, since they retain the same place of articulation after the change. == Productivity ==