Japanese Romanization Quick Reference

Rules for writing Japanese words in romaji with correct macrons and formatting.

Long Vowels - When to Use Macrons

USE Macron (ō, ū, ā, ē)

Long o (おう/オウ, おお/オオ):

Tōkyō (東京)
Kyōto (京都)
Ōsaka (大阪)
rōmaji (ローマ字)
shōgun (将軍)
daimyō (大名)
kendō (剣道)
judō (柔道)
shōyu (醤油)
tōfu (豆腐)

Long u (うう/ウウ, う extending vowel):

shūmatsu (週末)
gakkō (学校)
ryūgaku (留学)
Ryūkyū (琉球)
sūji (数字)

Long a (ああ/アア):

okāsan (お母さん)
obāsan (おばあさん)

Long e (ええ/エエ, えい sometimes):

onēsan (お姉さん)
sēfuku (制服) - but see exceptions below

DO NOT Use Macron

Long ii - always double i:

Niigata (新潟) - not Nīgata
oniisan (お兄さん) - not onīsan
ojiisan (おじいさん) - not ojīsan
chiisai (小さい) - not chīsai

Morpheme boundaries (meaningful units meeting):

koushi (子牛) - ko + ushi, not kōshi
otouto (弟) - can also be otōto depending on context

Dictionary form verb endings (-ou, -uu):

omou (思う) - not omō
tou (問う) - not tō
nuu (縫う) - not nū

Hyphens - When to Use

Geographic Terms (Jurisdictions)

Suffix	Example
-to (都)	Tōkyō-to
-fu (府)	Ōsaka-fu, Kyōto-fu
-ken (県)	Aichi-ken, Niigata-ken
-shi (市)	Yokohama-shi, Nagoya-shi
-ku (区)	Shibuya-ku, Chiyoda-ku
-chō/machi (町)	Ogawa-machi, Yūraku-chō
-mura/son (村)	Ogasawara-mura
-eki (駅)	Tōkyō-eki, Shibuya-eki

Exception: Hokkaidō - always one word, no hyphen

Geographic features - NO hyphen:

Fujisan (富士山)
Sumidagawa (隅田川)
Biwako (琵琶湖)

Titles and Honorifics After Names

Suffix	Example
-san	Tanaka-san
-sama	Tanaka-sama
-kun	Nakamura-kun
-chan	Non-chan
-sensei	Yamamoto-sensei (or Yamamoto Sensei)
-shi (氏)	Haido-shi
-ke (家)	Tokugawa-ke

Special Suffixes

Suffix	Example
-teki (的)	Nihon-teki (日本的)
-gata (型)	Honkon-gata (香港型)
-shiki (式)	Tanaka-shiki
-ryū (流)	Urasenke-ryū
-sei (製)	Nihon-sei
-san (産)	Shizuoka-san

Phonetic Changes in Compounds

When combining causes sound changes:

kabushiki-gaisha (株式会社)
fūfu-genka (夫婦喧嘩)
Yamato-damashii (大和魂)

Word Division

Write as ONE Word

Common compounds:

ukiyoe (浮世絵)
origami (折り紙)
sashimi (刺身)
tempura (天ぷら)
karate (空手)
samurai (侍)
tsunami (津波)
sake (酒)

Prefixes that attach:

daimyō (大名)
shinkansen (新幹線)
otanjōbi (お誕生日)

Suffixes that attach:

keizaiteki (経済的)
seibutsugaku (生物学)
Bukkyō (仏教)

Write as SEPARATE Words

Modifiers with independent meaning:

waga kuni (我が国)
kono machi (この町)

Titles before names:

Meiji Tennō (明治天皇)
Sei Sabieru (聖サビエル)

Prefixes with proper names:

Dai Nippon Teikoku (大日本帝国)
ko Kurosawa Akira (故黒澤明)

Apostrophe

Use between n + vowel or n + y:

shin’yō (信用)
san’en (三円)
hon’yaku (翻訳)
Ken’ichi (健一)
Shin’etsu (信越)
Man’yōshū (万葉集)

Capitalization

Always Capitalize

Personal names - each word:

Sugawara no Takasue no Musume
Tanaka Tarō
Kōbō Daishi

Geographic names - each word:

Nihon Rettō (日本列島)
Taiheiyō (太平洋)
Bōsō Hantō (房総半島)

Corporate/organization names - each word except particles:

Sensō o Kirokusuru Kai
Kokusai Bukkyō Bunka Gakujutsu Kaigi

Religions and sects:

Bukkyō, Shintō, Kirisutokyō
Zenshū, Jōdo Shinshū

Historical/cultural events - each word:

Dainiji Sekai Taisen (第二次世界大戦)
Sekigahara no Tatakai
Meiji Ishin
Kantō Daishinsai

Structures, buildings, roads:

Takamatsuzuka Kofun
Narita Kūkō
Kōshū Kaidō

Capitalize First Word Only

Titles of works (books, laws, artworks):

Tsurezuregusa (徒然草)
Asahi shinbun (朝日新聞)
Rōdō kumiaihō (労働組合法)
Fugaku sanjūrokkei (富嶽三十六景)

Historical periods:

Jōmon jidai (縄文時代)
Heianchō (平安朝)
Shōwaki (昭和期)

Never Capitalize

Particles - no, wa, o, e, ni, de, to, etc.:

Hotaru no hikari (蛍の光)
Sekigahara no Tatakai

Derivatives with common noun meaning:

gofuku (呉服) - not Gofuku
setomono (瀬戸物)
rōmaji (ローマ字)
bosuton baggu (ボストンバッグ)

和/漢/洋 compounds (unless referring to nation/language):

washitsu (和室), yōshu (洋酒), kanpō (漢方)
But: Wa-Ei jiten (和英辞典) - refers to languages
But: Wakō (和寇) - refers to national affiliation

Derivatives of Proper Names - Capitalize

When used as proper names:

Nihonjin (日本人)
Nihongo (日本語)
Eigo (英語)
Nihonshi (日本史)
Bukkyōto (仏教徒)

Common Words Reference

Japanese	Correct	Incorrect
東京	Tōkyō	Tokyo
京都	Kyōto	Kyoto
大阪	Ōsaka	Osaka
柔道	jūdō	judo
剣道	kendō	kendo
相撲	sumō	sumo
豆腐	tōfu	tofu
醤油	shōyu	shoyu
抹茶	matcha	-
侍	samurai	-
将軍	shōgun	shogun
大名	daimyō	daimyo
芸者	geisha	-
神道	Shintō	Shinto
仏教	Bukkyō	-
茶道	sadō/chadō	-
華道	kadō	-
武士道	bushidō	bushido
空手	karate	-
合気道	aikidō	aikido

Country/Language Abbreviations

Hyphenate when combining:

Nichi-Ro (日露) - Japan-Russia
Wa-Ei (和英) - Japanese-English
Nichi-Bei (日米) - Japan-US

But contractions are one word:

Nitchū (日中) - Japan-China
Nikka (日華) - Japan-China (historical)

Technical Identifiers in Code and Config Files

CRITICAL RULE: Proper romanization and capitalization ALWAYS take priority over programming naming conventions.

Apply Romanization to ALL Contexts

Use correct macrons and capitalization in:

JSON keys and values
Variable names
Attribute identifiers
Database field names
API parameters
File names

Examples

Correct approach:

attribute_name: "Shōgun-rank" (not "shogun-rank")
category: "Ryū" (not "Ryu")
location_id: "Tōkyō-station" (not "tokyo-station")
user_title: "Daimyō" (not "Daimyo")

Even in kebab-case or snake_case:

skill-type: "Kendō" ✓ (not "kendo")
power_source: "Shintō" ✓ (not "shinto")
npc-class: "Ōkami" ✓ (not "okami")

Capitalization Priority

Follow romanization capitalization rules, not code conventions:

Proper nouns stay capitalized: Use "Nihonjin" not "nihonjin"
Category names capitalized: Use "Bukkyō" not "bukkyo" for religion types
Common nouns lowercase: Use "sake" for the drink, "samurai" for warriors

Don’t Sacrifice Accuracy for Convention

Wrong thinking: “It’s a variable name, so make it lowercase” Right thinking: “It’s a Japanese proper noun, so capitalize it correctly”

Programming style guides bow to linguistic accuracy when dealing with non-English terms that have established romanization standards.