Long Vowels

In Japanese, long vowels, or "long sounds," chouon 長音, refer to vowels pronounced for twice as long than normal. See also: mora. The opposite are short vowels, or "short sounds," tan'on 短音.

For example, ko こ has a short vowel, while kou こう, koo こー, and koo こぉ have long vowels.

• Orthography
  
  • 長音化
  • 短母音化
  • Mimetic Words

Orthography

The way long vowels are represented in Japanese is a bit complicated.

In katakana words, the ー prolonged sound mark, also called chouonpu 長音符, "long sound mark," is used.

• koohii
  コーヒー
  Coffee.
• keeki
  ケーキ
  Cake.

Otherwise, a, i, u, e, あいうえ are used.

• okaasan
  おかーさん
  おかあさん
  お母さん
  Mother.
• oniisan
  おにーさん
  おにいさん
  お兄さん
  Brother.
• fuufu
  ふーふ
  ふうふ
  夫婦
  Husband and wife.
• oneesan
  おねーさん
  おねえさん
  お姉さん
  Sister.

長音化

Some syllables in Japanese are spelled as diphthongs, composed of two different vowels, ~ei and ~ou, but are pronounced in practice as just one long sound, ~ee and ~oo. For example:

• sensei
  せんせい
  せんせー
  先生
  Teacher.
• otousan
  おとうさん
  おとーさん
  お父さん
  Father.

Even though in the dictionary the words have ~ei and ~ou, in practice people generally don't pronounce the ~i and ~u separately, they just make the ~e and ~o sound longer than normal.

This process is called chouonka 長音化, literally "long sound-fication."

In such cases, deliberately spelling the word with a prolonged sound mark implies that the character speaks noticeably different from normal. In a very relaxed, or drunk way, or speaking like a little child, that kind of stuff.

短母音化

In some cases, a long vowel is pronounced instead as a short vowel. A phenomenon termed tanboinka 短母音化, "short vowel-fication." This means that a long syllable, which should take two mora to pronounce, takes instead only one mora to pronounce.

Since this change in pronunciation may be impossible to perceive in words spelled with kanji, when it happens the words may be unusually spelled with hiragana, or maybe even spelled with katakana, instead.

For example:

• hontou
  ほんとう
  ほんとー
  本当
  Really.
  • Four mora: ho-n-to-u.
• honto
  ホント
  (same meaning.)
  • Three mora: ho-n-to.
• gakkou
  がっこう
  がっこー
  学校
  School.
  • Four mora: ga-k-ko-u.
• gakko
  ガッコ
  (same meaning.)
  • Three mora: ga-k-ko.

One example of usage:

• gakko ikitakunai
  ガッコ行きたくない
  [I] don't want to go to school.

Mimetic Words

Some onomatopoeia and mimetic words feature the prolonged sound mark despite being spelled with hiragana. For example:

• shiin
  しーん
  *silence*
• nyaa
  にゃー
  Meow.