Editing Japanese pitch accent (section)

===Accent nuclei, defective morae and compound-induced accent shifts===
An {{nihongo|"accent nucleus" or "kernel"{{sfnp|Labrune|2012|pp=174, 179}}|アクセント核|akusento kaku}} is another name for an accented mora, a mora that carries a high tone and is followed by a mora with a low tone. In other words, the precipitous drop in pitch occurs right at the boundary between the accent nucleus and the mora immediately after it. Unaccented words (of the ''heiban'' type) do not have an accent nucleus.

Unlike regular morae or 自立拍 (''jiritsu haku'' "autonomous beats"), defective morae{{sfnp|Labrune|2012|p=201}} or 特殊拍 (''tokushu haku'' "special beats") cannot generally be accent nuclei. They historically arose through various processes that limited their occurrences and prominence in terms of accent-carrying capability. There are four types of them:
*The {{nihongo|moraic nasal|撥音/撥ねる音|hatsuon/haneru on|/N/, spelt ん or ン}}: derived from [[Middle Chinese]] coda consonants (/n/ and /m/) (e.g.: /kaN/; /wemu/ > /eN/), but also arose naturally through ''[[onbin]]'' (e.g.: /yomite/ > /yoNde/)
*The {{nihongo|moraic obstruent|促音/詰まる音|[[sokuon]]/tsumaru on|/Q/, spelt っ or ッ}}: mainly arose through ''onbin'' (e.g.: /katite/ > /kaQte/) or through consonant assimilation (e.g.: /setpuku/ > /seQpuku/)
*The {{nihongo|lengthening mora|引（き）音/長音|hikion, in'on/chōon|/R/, spelt あ/ア, い/イ, う/ウ, え/エ, お/オ or ー}}: arose through consonant losses (e.g.: /kakasaN/ > /kaRsaN/), vowel shifts or vowel assimilation during [[Late Middle Japanese]] (e.g.: /eu/ > /joR/; /joũ/ > /joR/)
*The morphologically bound /i/ (/J/, written in kana as い/イ): derived from a Middle Chinese [[offglide]] (e.g.: /taJ/; /tuJ/) or arose through ''onbin'' (e.g.: /kakisiro/ > /kaJsiro/)

While the accent patterns of single words are often unpredictable, those of compounds are often rule-based. Take the suffix 市 (''-shi''), for example. When compounding with a place name to form a city name, the accent nucleus of the resulting compound is usually immediately before 市 itself:
*千葉 (''[[Chiba (city)|Chiba]]''): HꜜL > 千葉市 (''Chiba-shi'' "Chiba City"): L-HꜜL /tibaꜜsi/
But if the mora before 市 is defective, the accent must shift one mora backward:
*白山 (''[[Hakusan, Ishikawa|Hakusan]]''): HꜜL-L-L > 白山市 (''Hakusan-shi'' "Hakusan City"): L-H-HꜜL-L /hakusaꜜNsi/
*西条 (''[[Saijō, Ehime|Saijō]]''): HꜜL-L-L > 西条市 (''Saijō-shi'' "Saijō City"): L-H-HꜜL-L /saJzjoꜜRsi/
*仙台 (''[[Sendai]]''): HꜜL-L-L > 仙台市 (''Sendai-shi'' "Sendai City"): L-H-HꜜL-L /seNdaꜜJsi/

A defective mora can be an accent nucleus only if the mora following it is also defective:<ref>{{cite book|title=Handbook of Japanese Phonetics and Phonology|date=2015|publisher=Walter de Gruyter}}</ref>
*ロンドンっ子 (''Rondon-kko'' "Londoner"): L-H-H-HꜜL-L /roNdoNꜜQko/
*東京っ子 (''Tōkyō-kko'' "Tokyoite"): L-H-H-HꜜL-L /toRkjoRꜜQko/
*現代っ子 (''gendai-kko'' "modern person"): L-H-H-HꜜL-L /ɡeNdaJꜜQko/

====Compoundified compound nouns vs noncompoundified compound nouns====
In general, Japanese utterances can be syntactically split into discrete phrases (known in the [[Hashimoto Shinkichi|Hashimoto]] school of grammar as {{nihongo||文節|bunsetsu}}<ref name=DJR>''[[Daijirin]]''</ref>). For example, the utterance 母が料理をして父が皿を洗います (''Haha-ga ryōri-o shite chichi-ga sara-o arai-masu'' "My mother cooks and my father washes the dishes") can be subdivided into the following phrases:
*母が (''haha-ga'')
*料理を (''ryōri-o'')
*して (''shite'')
*父が (''chichi-ga'')
*皿を (''sara-o'')
*洗います (''arai-masu'')
The general structure of these phrases is that a syntactically [[free morpheme]] is followed by one or more syntactically [[bound morpheme]]s. Free morphemes are nouns, adjectives and verbs, while bound morphemes are particles and auxiliaries. In the above utterance, the free morphemes are 母, 料理, して, 父, 皿, and 洗い while the bound ones are が, を and ます. The accent pattern of the entire utterance could be something like this:

{| class="wikitable" style="text-align:center"
|ha-ha-ga
|ryo-o-ri-o
|shi-te
|chi-chi-ga
|sa-ra-o
|a-ra-i-ma-su
|-
|HꜜL-L
|HꜜL-L-L
|L-H
|HꜜL-L
|L-H-H
|L-H-H-HꜜL
|}

Ideally, each phrase can carry at most one accent nucleus (in the above example, '''''ha'''-ha-ga'', '''''ryo'''-o-ri-o'', '''''chi'''-chi-ga'' and ''a-ra-i-'''ma'''-su''), and such accent nucleus is based solely on the lexical accent nucleus of the free morpheme of that phrase (bound morphemes do not have lexical accent patterns, and whatever accent patterns they do have is dependent on those of the free morphemes they follow). However, the situation becomes complicated when it comes to compound nouns.

When multiple independent nouns are placed successively, they syntactically form a compound noun. For example:
*第 (''dai'') + 一次 (''ichiji'') + 世界 (sekai) + 大戦 (''taisen'') > 第一次世界大戦 (''Dai-ichiji-Sekai-Taisen'' "World War I")
At the phrasal level, compound nouns are well contained within a phrase, no matter how long they are. Thus, the utterance ヨーロッパは第一次世界大戦では主戦場となった (''Yōroppa-wa Dai-ichiji-Sekai-Taisen-de-wa shusenjō-to natta'' "Europe was the main theater of war in World War I") is subdivided into phrases as follows:
*ヨーロッパは (''Yōroppa-wa'')
*第一次世界大戦では (''Dai-ichiji-Sekai-Taisen-de-wa'')
*主戦場と (''shusenjō-to'')
*なった (''natta'')
As ''Dai-ichiji-Sekai-Taisen-de-wa'' is an entire phrase in itself, it should ideally carry at most one accent nucleus, the lexical accent nucleus of the free compound noun ''Dai-ichiji-Sekai-Taisen''. In actuality, ''Dai-ichiji-Sekai-Taisen'', as a compound noun, is capable of carrying more than one accent nucleus. While still being a syntactic compound, its components might not be solidly "fused" together and still retain their own lexical accent nuclei. Whether ''Dai-ichiji-Sekai-Taisen'' should have one nucleus of its own, or several nuclei of its constituents, is a matter of whether it is a "compoundified compound noun" (複合語化複合名詞 ''fukugōgoka fukugō meishi'') or "noncompoundified compound noun" (非複合語化複合名詞 ''hifukugōgoka fukugō meishi'').<ref>{{cite book|last1=Kubozono|first1=Haruo|title=日本語複合語の意味構造と韻律構造|date=1987|publisher=[[Nanzan University]]}}</ref> The "compoundification" status of a compound noun is lexical, meaning that whether such compound noun is long or short, or simple or complex, is not relevant to whether it is "compoundified" or not. A [[yojijukugo]] such as 世代交代 (''sedai-kōtai'' "change of generation") may be treated as "compoundified," with a single accent nucleus:<ref name=nhkguide>{{cite book|last1=Tanaka|first1=Ishiki|title=複合名詞の発音とアクセント|date=2017|publisher=NHK}}</ref>

{| class="wikitable" style="text-align:center"
!世代交代
|-
|se-da-i-ko-o-ta-i
|-
|L-H-H-HꜜL-L-L
|}

Meanwhile, a different four-kanji compound noun, 新旧交代 (''shinkyū-kōtai'' "transition between the old and the new"),<ref name=nhkguide /> is treated as "noncompoundified", and retains the lexical accent nuclei of its constituents (in this case 新旧 and 交代):

{| class="wikitable" style="text-align:center"
!新旧 + 交代
|-
|shi-n-kyu-u + ko-o-ta-i
|-
|HꜜL-L-L + H-H-H-H
|}

Some compound nouns, such as 核廃棄物 (''kaku-haikibutsu'' "nuclear waste"), can be, on a preferential basis, either "compoundified" or "noncompoundified":

{| class="wikitable" style="text-align:center"
!核廃棄物
!核 + 廃棄物
|-
|ka-ku-ha-i-ki-bu-tsu
|ka-ku + ha-i-ki-bu-tsu
|-
|L-H-H-H-HꜜL-L
|HꜜL + L-H-HꜜL-L
|}

For "noncompoundified" compound nouns, which constituents should be allowed for may also vary. For example, the above 第一次世界大戦:

{| class="wikitable" style="text-align:center"
!第一次 + 世界大戦
!第 + 一次 + 世界大戦
|-
|da-i-i-chi-ji + se-ka-i-ta-i-se-n
|da-i + i-chi-ji + se-ka-i-ta-i-se-n
|-
|HꜜL-L-L-L + L-H-H-HꜜL-L-L
|HꜜL + L-HꜜL + L-H-H-HꜜL-L-L
|}