PACLIC 18, December 8th-10th, 2004, Waseda University, Tokyo

Effects of Mora Phonemes on Japanese Word Accent

Yasuyo TOKUHIRO Shizuo HIKI Graduate School of Japanese Applied Waseda University Linguistics, Waseda University 2-579-15 Mikajima 1-7-14, Nishi-Waseda, Shinjuku-ku Tokorozawa, 359-1192 Japan Tokyo, 169-8050 Japan [email protected] [email protected]

Abstract Effects of mora phonemes on Japanese word accent was analyzed statistically, utilizing a set of about 124,000 frequently used common nouns derived from the Japanese Word Dictionary edited by EDR (the Japan Electronic Dictionary Research Institute, Ltd., Japan). In this analysis, Japanese syllable was defined as preceding consonant (+semi-vowel) +following vowel, accompanied / not accompanied by mora phoneme. Mora phonemes adopted here were elongated portion of vowel: /H/, chocked sound: /Q/, syllabic nasal: /N/, and /i/ portion of diphthongs: /I/. The average ratio of attachment of accent to vowel type syllables was 13% and to semi-vowel +vowel type syllables 16%. In both types, the difference according to the kind of following vowels was not significant. As for the effect of mora phonemes, the ratios of accent attached to the syllables accompanied by mora phonemes were about several percents higher than their average for any kind of following semi-vowels and vowels. The average ratio of accent attached to vowel and semi-vowel +vowel type syllables was 14%, but in syllables of any kind of preceding consonants accompanied by mora phoneme, the ratios were more than several percents higher than the average. The words which involve the mora phonemes were categorized by each kind of mora phoneme, and compiled into the list in the order of Japanese syllabary, and the lists of different number of syllables composing each word in the order of Japanese syllabary. In addition, the list for retrieving the possible candidate words which could be replaced if the mora phonemes were missing through imperfect hearing or pronouncing. Those databases are useful for language teaching and speech training, as well as for basic research on speech processing.

1 Introduction From the Japanese Word Dictionary edited by EDR (Japan Electronic Dictionary Research Institute, Ltd., Japan), about 300,000 common nouns were extracted, and the foreign words which occupied 15% of them were deleted. About 80% of the inventory of 260,000 remaining words belonged to the groups of the words having the same pronunciation (homonyms), as many of the words were listed separately according to the precise differences in meanings or notations in the “Headwords” of the EDR dictionary. So, the groups of homonyms in the inventory were sub-divided step by step into the groups having the same “Concept Identifier” (the minimum unit of the concept of word), “Headconcept” (finer unit than the head words), then, “Headword”, and a representative word for each of the sub-groups were extracted, based on higher “Concept Occurrence Frequency,” in each of the steps. In case that the "Concept Occurrence Frequency" was even, a word which contains larger number of Chinese character was selected. By defining homonyms step by step wider in this way, the original word inventory was consolidated into the resulting set of about 124,000 words. This corresponded to about 50% of the original Headwords. This word set was used for the statistical analyses on the relationship between the word accent and syllable structure, with special regard to the effects of mora phonemes. 2 Statistical Properties of Japanese syllables 2.1 Structure of Japanese homonyms The words not having homonyms were about 81,000 words, which corresponds to about 65% of the total number of words. Consequently, the remaining about 35% of the words belonged to one of the groups of homonyms. The number of words in each of the groups of homonyms ranged from two to 37. The number of the groups decreased as the number of words in each of the groups increased, and such a large number of word set demonstrated that they were closely inversely proportional. The number of syllables which compose a word decreased as the number of words in the homonymous group increased. In the 20 groups with more than 22 words, 80% of them were two syllable words, and the rest one syllable words.

2.2 Defining the Japanese syllables and mora phonemes In this analysis, Japanese syllable was defined as preceding consonant (+semi-vowel) +following vowel, accompanied / not accompanied by mora phoneme. The kind of preceding consonants adopted here were /#/ (not preceded by consonant), /s/, /k/, /z/, /r/, /g/, /h/, /b/, /n/, /m/, /p/, and /d/ (for syllables /da, de, do/ only). Vowels are /a/, /i/, /u/, /e/, and /o/. Semi-vowels are /y/ (in /ya/, /yu/ and /yo/), and /w/ (in /wa/). The mora phonemes were defied here as elongated portion of vowel (denoted as /H/), syllabic nasal portion (/N/), choked sound portion proceeding to the unvoiced consonants (/Q/), and diphthongized vowel /i/ portion in ai, ei, oi and ui (/I/). As the down skip of word accent in Tokyo dialect is not attached to the mora phonemes, the syllable by this definition is the minimum segment to which a word accent can be attached.

2.3 Occurrence frequency of consonants and mora phonemes This consolidated word set contained 436,000 syllables followed by only vowel, and 55,000 syllables followed by semi-vowel + vowel, 491,000 syllables in total. The occurrence frequency of semi-vowel +vowel type syllables were about 1/10 of the vowel type syllables in average. The values were close each other types in the preceding consonant as /z/, while, preceding consonant as /m/ nearly 1/100. As for the occurrence frequency of kind of preceding consonants, /k/ was 100,000 syllables, /#/ 72,000 syllables, /s/ 71,000 syllables and /t/ 51,000 syllables. Occurrence frequencies of /z/, /r/, /g/, /h/, /b/, /n/, and /m/ were as few as 1/5 of /k/. In the 36 kinds of syllables included in the 20 groups of large number of homonyms, preceding consonants were only /k/ and /s/, both of them being 50%. Those occurrence frequencies of /k/ and /s/ were very large compared with their average of both 1/5 in this consolidated word set of 491,000 syllables. It is also noticeable that the preceding consonants /#/ and /t/ which had almost the same large occurrence frequencies as /k/ and /s/ were not included. Relationships between occurrence frequencies of vowel type syllables vs. semi-vowel +vowel type syllables are shown, by categorizing by kind of vowels and preceding consonants, in the left and right parts of Figure 1, respectively. The mora phoneme /H/ was attached to half of the syllables, and /N/ to 1/6 of them. Occurrence frequency of 1/2 of mora phoneme /H/ was too large compared with the average of 1/9 in the word set. Furthermore, all of them were kanji (Chinese character in Japanese orthography). This suggests the influence of the original Chinese pronunciation, as the ratio was much higher than the average ratio of kanji words in this word set.

3 Effect of mora phonemes on the word accent

3.1 Number of syllables accompanied by mora phoneme

In this consolidated word set, the number of syllables accompanied by the mora phonemes were /N/; 61,000, /H/; 47,000, /Q/; 5,500 for vowel type syllables, and /N/; 1,000, /H/; 26,000, and /Q/; 500 for PACLIC 18, December 8th-10th, 2004, Waseda University, Tokyo

semi-vowel +vowel type syllables. Occurrence probability of semi-vowel +vowel type syllables accompanied by mora phonemes was as high as 1/2, although the average occurrence probability of that type of syllable was 1/10. Among them, 3/4 was /yo/ and 1/4 was /yu/, which were comparable to the occurrence probability of the vowel type syllables.

3.2 Occurrence frequency of accented syllables 3.2.1 Semi-vowels and vowels In the occurrence frequencies of the vowel type syllables, /a/, /i/ and /o/ were larger and /e/ and /u/ were smaller, but the difference was within 1/2. On the other hand, in the semi-vowel +vowel type syllables, the difference was larger, and the number decreased in the order of /yo/, /yu/ and /ya/ by 1/2 steps. Average ratio of attachment of accent to vowel type syllables was 13% and semi-vowel +vowel type syllables 16%. In both cases, the difference according to the kind of following vowels was not significant. However, the ratios of accent attached to the syllables accompanied by mora phonemes were several percents higher than the average of 16% for vowel type syllables and 16% for semi-vowel +vowel type syllables for all kinds of following semi-vowels and vowels. Relationships between occurrence frequencies of syllables with accent vs. without accent classified by not accompanied or accompanied by mora phonemes, /H/, /N/, /Q/ and /I/, are shown, for each kind of vowel type and semi-vowel +vowel type syllables, in Figure 2. This may be related to the fact that the durations of the syllables accompanied by mora phonemes are longer and easier to lower the voice pitch, at the same time, the change in voice pitch is easier to be perceived.

3.2.2 Preceding consonants The average ratio over vowel type and semi-vowel +vowel type syllables was 14%, and the ratios in the syllables of any kind of preceding consonants accompanied by mora phoneme were more than several percents larger than the average. In the syllables accompanied by /Q/, the increase ranged up to twice of the average, 28%, and there was a tendency that syllables preceded by /g/, /k/, /s/ and /b/ to have more probability of accent attachment. Relationships between occurrence frequencies of syllables with accent vs. without accent classified by not accompanied or accompanied by mora phonemes, /H/, /N/, /Q/ and /I/, are shown for each kind of preceding consonants in Figure 3. Examples of the pairs of words involving the same syllable without accent vs. with accent when accompanied by mora phoneme, which cause above mentioned statistical property, are shown for each kind of mora phonemes and for each kind of semi-vowels and vowels in Table 1. An example of the group of words involving the same syllable with or without accent, or with or without accent when accompanied by mora phoneme, is shown for each kind of the mora phonemes in Table 2.

4 Application to language education 4.1 Confusion caused by imperfection in mora phonemes Group of words which involve the same syllable but accompanied by different kind of mora phonemes, as shown in Table 3, are found frequently in Japanese. Imperfection in identifying or pronouncing mora phoneme causes confusion among the words in those groups. Among the words in those groups, especially the pairs of words involving the same syllable not accompanied vs. accompanied by mora phoneme but both with accent or without accent require reasonable capability in the mora phonemes, as the accent information is not available. There are many of such pairs even among the frequently used words, as shown in Table 4. 4.2 Database for editing teaching materials The Japanese homonyms were compiled into the lists categorized by the number of words in the group of homonyms, or by the number of syllables composing a word, and arranged in the order of Japanese syllabary. The words which involve the mora phonemes were categorized by each kind of mora phonemes, or by different number of syllables composing each word, and compiled into the lists in the order of Japanese syllabary. Also compiled was the list of the possible candidate words which could be replaced if the mora phonemes in the intended words were missing through imperfect identifying or pronouncing in the course of Japanese speech learning. Those pairs which are useful as the teaching materials of Japanese speech can be retrieved systematically in those database.

5 Conclusion Among the 491,000 syllables involved in the word set used for this statistical analysis, syllables accompanied by mora phoneme occupied 30% of them. In addition, the syllables accompanied by mora phoneme appeared frequently in the words in the sets of homonyms, which were comprised by very large number of words in the set. High occurrence ratio of mora phonemes in the syllables, their significant effects on word accent, and their role in composing a large number of homonyms are important features characteristic of Japanese language. As those databases of Japanese homonyms and Japanese words involving mora phonemes were compiled based on the detailed statistical analysis on the nature of Japanese homonyms and the effect of mora phonemes on word accent, they will serve as an useful tool in language teaching, as well as for basic research on language processing.

NUMBER OF SYLLABLES NUMBER OF SYLLABLES GROUPED BY FOLLOWING VOWELS AND SEMIVOWELS GROUPED BY PRECEDING CONSONANTS 100,000 CV = CyV 100,000 CV = CyV = 10 * CyV CV + CyV = 100,000 CV + CyV = 100,000 All 50,000 CV：CyV 50,000 s 20000 Co：Cyo 20,000 # 10,000 Ca：Cya 10,000 s) = 100 * CyV s) z = 100 * CyV e

Cu：Cyu e l 10000 l 10,000 ｋ b

b t a a l l l l r y y s s (

(

V ｇ V y y C C 1,000 1,000 h b n m C: CONSONANTS C: CONSONANTS V: a, i, u, e, o V: a, i, u, e, o yV: ya, yu, yo yV: ya, yu, yo 100 Ce Ci 100 1,000 10,000 100,000 1,000,000 1,000 10,000 100,000 1,000,000 CV (syllables) CV (syllables)

Figure 1. Relationships between occurrence frequencies of vowel type syllables vs. semi-vowel +vowel type syllables, categorized by kind of vowels (left) and preceding consonants (right). PACLIC 18, December 8th-10th, 2004, Waseda University, Tokyo

NUMBER OF SYLLABLES GROUPED BY FOLLOWING VOWELS AND SEMI-VOWELS 100,000 MORA PHONEME /H/, /N/, /Q/, /I/ 13% CV ACCOMPANIED BY CVN

g) MORA PHONEME

o 10,000 CVH

L 16%

, CyVH s e l CyV b

a CVI ll y

s CVQ NOT ACCOMPANIED ( 1,000 T BY MORA PHONEME N E C

C CyVN A

H CyVQ T I 100 W 13% Average of V C: CONSONANTS V: a, i, u, e, o 16% Average of yV yV: ya, yu, yo 10 100 1,000 10,000 100,000 1,000,000 WITHOUT ACCENT(syllables, Log)

NUMBER OF SYLLABLES NUMBER OF SYLLABLES GROUPED BY FOLLOWING VOWELS AND SEMI-VOWELS GROUPED BY FOLLOWING VOWELS AND SEMI-VOWELS 100,000 MORA PHONEME /H/: 100,000 MORA PHONEME /Q/: ELONGATED PORTION OF VOWEL 13% CHOKED SOUND 13% CV CV ACCOMPANIED BY

CVH g)

g) MORA PHONEME /H/ Ca o 10,000 Ca o 10,000 L 16%

L 16% Ci , Ci CoH , CyVH Cu s ACCOMPANIED BY Cu s e Co Co l

e CyoH l CyV b MORA PHONEME /Q/ CyV b a

CeH l l a Ce l Ce l y y s CVQ Cyo s CyuH

Cyo ( ( NOT ACCOMPANIED

1,000 1,000 T Cya NOT A CCOMPANIED

T Cya CuH BY MORA PHONEME N Cyu N CaQ Cyu E BY MORA PHONEME E CiH CeQ

C CiQ . . CC C

A CoQ

CaH A

H CyVQ H T I

T 100 I

100 W CyaQ

W CuQ 13% Average of V 13% Average of V CyuQ C: CONSONANTS C: CONSONANTS CyaH V: a, i, u, e, o V: a, i, u, e, o CyoQ 16% Average of yV yV: ya, yu, yo 16% Average of yV yV: ya, yu, yo 10 10 100 1,000 10,000 100,000 1,000,000 100 1,000 10,000 100,000 1,000,000 WITHOUT ACCENT(syllables, Log) WITHOUT ACCENT(syllables, Log)

NUMBER OF SYLLABLES GROUPED BY FOLLOWING VOWELS AND SEMI-VOWELS NUMBER OF SYLLABLES 100,000 MORA PHONEME /N/: GROUPED BY FOLLOWING VOWELS SYLLABIC NASAL 13% 100,000 MORA PHONEME /I/: CV i PORTION OF DIPHTHONGS ai, ei, oi, ui 13% CV ACCOMPANIED BY CVN g) g)

o 10,000 Ca

MORA PHONEME /N/ o L 16% Ci ACCOMPANIED Ca 10,000 L , Cu Ci , s BY MORA PHONEME /I/

Co s Cu e CaN l CeN . . . CyV e l b Co b a

l CiN Ce l a

l CVI y NOT ACCOMPANIED l Ce

CoN y s Cyo ( CaI s 1,000 NOT ACCOMPANIED CuN Cya BY MORA PHONEME ( T 1,000 T N Cyu BY MORA PHONEME N E CoI E C C

CyVN CC A

CeI A

H CyuN H T I

100 T I 100 CuI W CyaN 13% Average of V W 13% Average of V C: CONSONANTS CyoN V: a, i, u, e, o C: CONSONANTS 16% Average of yV yV: ya, yu, yo V: a, u, e, o 10 10 100 1,000 10,000 100,000 1,000,000 100 1,000 10,000 100,000 1,000,000 WITHOUT ACCENT(syllables, Log) WITHOUT ACCENT(syllables, Log)

Figure 2. Relationships between occurrence frequencies of syllables with accent vs. without accent classified by not accompanied or accompanied by mora phonemes, /H/, /N/, /Q/ and /I/, for each kind of vowel type and semi-vowel +vowel type syllables. NUMBER OF SYLLABLES GROUPED BY PRECEDING CONSONANTS 0.14 10,000 MORA PHONEME /H/, /N/, /Q/, /I/ sｋ ｋ s t t # h # ｇz z m r bd r bn ｇ g) ACCOMPANIED BY n m h

o 1,000

L MORA PHONEME d , s

e w l b

a NOT ACCOMPANIED ll

y p s BY MORA PHONEME ( 100

T p

N w E C C A

H T I 10 W

V: a, i, u, e, o 0.14 Average of V+yV yV: ya, yu, yo 1 10 100 1,000 10,000 100,000 WITHOUT ACCENT(syllables, Log)

NUMBER OF SYLLABLES NUMBER OF SYLLABLES GROUPED BY PRECEDING CONSONANTS GROUPED BY PRECEDING CONSONANTS 14% 14% 10,000 MORA PHONEME /H/: 10,000 MORA PHONEME /Q/: ｋ ｋ ELONGATED PORTION OF VOWEL s ELONGATED PORTION s s t # t # ｋ .. .m. .. ｇ. .r . .m. .. ｇ. .r t z z g) # . b g) . b o z o h L 1,000 h h L 1,000

r n

, n d d , s ｇ s ACCOMPANIED BY d e e

l b m w l w b n b MORA PHONEME /Q/ a a ll ACCOMPANIED BY NOT ACCOMPANIED ll ｋ.s NOT ACCOMPANIED y y ｇ s s

, MORA PHONEME /H/ BY MORA PHONEME , h# BY MORA PHONEME Y Y r.b ( 100

p p ( 100 t p T T z N N n E E d m CC CC A A

H H T 10 T I w I 10 W W pw

14%Average of V+yV 14% Average of V+yV 1 1 10 100 1,000 10,000 100,000 10 100 1,000 10,000 100,000 WITHOUT ACCENT (X, syllables, Log) WITHOUT ACCENT (X, syllables, Log)

NUMBER OF SYLLABLES NUMBER OF SYLLABLES GROUPED BY PRECEDING CONSONANTS GROUPED BY PRECEDING CONSONANTS 13% 14% 10,000 10,000 MORA PHONEME /N/: MORA PHONEME /I/: ｋ ELONGATED PORTION OF ｋ ELONGATED PORTION OF VOWEL s st t # VOWEL ｋ. .. m. .ｇ m r # s . . . . .r z ｇ

z g) b g) . b # o h

o ｋ n

L 1,000 L 1,000 t h s , b. . n , h. d g z s ACCOMPANIED BY

s d t e l e d m l n d w

b MORA PHONEME /I/

b r w

a ｇ a ll

ll ACCOMPANIED BY z y NOT ACCOMPANIED

y NOT ACCOMPANIED r s

s h

, MORA PHONEME /N/ b , BY MORA PHONEME n BY MORA PHONEME Y Y

( m

( 100 100 p p # T

T p N N E E w CC CC w A A

H H T T 10 I 10 I W W p

14% Average of V+yV 13% Average of V V: a, u, e, o 1 1 10 100 1,000 10,000 100,000 10 100 1,000 10,000 100,000 WITHOUT ACCENT (X, syllables, Log) WITHOUT ACCENT (X, syllables, Log)

Figure 3. Relationships between occurrence frequencies of syllables with accent vs. without accent classified by not accompanied or accompanied by mora phonemes, /H/, /N/, /Q/ and /I/, for each kind of preceding consonants. PACLIC 18, December 8th-10th, 2004, Waseda University, Tokyo

Table 1. Examples of the pairs of words involving the same syllable without accent vs. with accent when accompanied by mora phoneme.

Word Phoneme Meaning /H/ 詩歌 si'Hka poetry /Q/ 末期 ma'Qki last period 鹿 sika deer 薪 maki firewood 数奇 su'Hki varied 一気 #i'Qki one breath 隙 suki unguarded moment 生き #iki freshness 英気 #e'Hki will 一件 #i'Qken an incident 易 #eki fortune telling 違憲 iken violation of a constitution 定期 te'Hki periodic 屈指 ku'Qsi outstanding 敵 teki competitor 櫛 kusi comb 謳歌 #o'Hka enjoy 決心 ke'QsiN determination 丘 #oka hillock 化身 kesiN incarnation 週 syu'H week 骨子 ko'Qsi crux 朱 syu yellowish red 腰 kosi waist 胡椒 kosyo'H pepper 厄介 ya'Qkai bothersome 古書 ko'syo secondhand book 夜会 yakai evening party

/N/ 看護 ka'Ngo to nurse /I/ 解釈 ka'Isyaku interpretation 篭 kago basket 呵責 kasyaku remorse 金属 ki'Nzoku metal 才気 sa'Iki intelligent 帰属 kizoku to be subordinate 先 saki tip 信教 si'NkyoH religion 粋 su'I excellent 市況 sikyoH market 洲 su sandbank 奮起 hu'Nki percolate 思い #omo'I feeling 蕗 huki butterbur 面 #o'mo surface 天気 te'Nki weather 謝意 sya'I gratitude 敵 teki competitor 紗 sya gossamer 春闘 syu'NtoH spring labor offensive 首位 syu'I primacy 種痘 syutoH vaccination 朱 syu yellowish red

所為 syo'I action 書 syo calligraphy

Table 2. Examples of the group of words involving the same syllable with or without accent, or with or without accent when accompanied by mora phoneme.

Word Phoneme Meaning /H/ 上司 zyo'Hsi chief /Q/ 一件 #i'Qken an incident 上梓 zyoHsi publish 一見 #iQken glimpse 女子 zyo'si woman 意見 #i'ken view 助詞 zyosi particle 違憲 #iken unconstitutionality

/N/ 寒気 ka'Nki cold /I/ 貝 ka'I shellfish 換気 kaNki ventilate 買い kaI buying 牡蠣 ka'ki oyster 課 ka' unit of an office 柿 kaki persimmon 蚊 ka mosquito Table 3. Examples of Group of words which involve the same syllable but accompanied by different kind of mora phonemes.

Word Phoneme Meaning 施工 sekoH construction 呼気 ko'ki exhalation 精巧 seHkoH elaborate 後期 ko'Hki latter term 成功 seHkoH success 好機 ko'Hki opportunity 選考 seNkoH select 高貴 ko'Hki nobility 閃光 seNkoH flash 婚期 ko'Nki marriageable age 専攻 seNkoH major 根気 koNki patience 線香 se'NkoH joss stick 克己 ko'Qki self-restraint 石膏 seQkoH gypsum 国旗 koQki national flag

席 se'ki seat 敵 teki competitor 籍 se'ki membership 咳 seki cough 提起 te'Hki proposition 定期 te'Hki periodic 世紀 se'Hki century 正規 se'Hki regular 天気 te'Nki weather 生起 se'Hki happen 転機 te'Nki opportunity to change 転記 teNki transfer 戦記 se'Nki record of war 鉄器 teQki ironware 石器 seQki stone implement 敵機 te'Qki enemy aircraft

補記 ho'ki supplementing 蕗 huki butterbur 箒 ho'Hki broom 付記 hu'ki additional remark 法規 ho'Hki regulations 風紀 hu'Hki discipline 放棄 ho'Hki abandon 富貴 hu'Hki wealth 本気 hoNki seriousness 奮起 hu'Nki rouse to action 発起 hoQki proposition 復帰 huQki return

Table 4. Examples of the pairs of words involving the same syllable not accompanied vs. accompanied by mora phoneme but both with accent or without accent.

Word Phoneme Meaning /H/ 装置 so'Hti installation /Q/ 一家 #i'Qka family 措置 so'ti measure 以下 #i'ka less than 周期 syu'Hki cycle 括弧 ka'Qko brackets 手記 syu'ki memorandum 過去 ka'ko pastness 報道 hoHdoH news 奪回 daQkai retake 歩道 hodoH sidewalk 打開 dakai breakthrough 訂正 teHseH correct 復旧 huQkyuH restoration 手製 teseH handicraft 普及 hukyuH spread

/N/ 管理 ka'Nri manage /I/ 大気 ta'Iki atmosphere 狩り ka'ri hunting 多岐 ta'ki diversified 文化 bu'Nka culture 廃棄 ha'Iki disposal 部下 bu'ka subordinate 破棄 ha'ki cancel 損失 soNsitu loss 在籍 zaIseki be enrolled 素質 sositu aptitude 座席 zaseki seat 瞬間 syuNkaN moment 大漁 taIryoH big catch 主観 syukaN subjectivity 多量 taryoH numerous