Definitions

Mora

A mora is the shortest unit of length in Japanese phonology. Every open syllable is a mora, long syllables are two moras, ん and っ are it's own moras too. A rule of thumb is that, when written in kana, each character represents a separate mora (with an exception of small ゃゅょ)

  • せんせい - 4 moras: せ　ん　せ　い
  • です - 2 moras: で　す
  • やさしい - 4 moras: や　さ　し　い
  • がっしょう - 4 moras: が　っ　しょ　う

Phrase

A phrase is part of a sentence which has it's own pitch accent. Contrary to common belief, pitch accent doesn't apply to words but to entire phrases in a sentence. A phrase usually consist of a core meaning word (usu. noun/verb/adjective) and it's prefixes, suffixes, particles, and conjugation endings.

Let's look at this sentence: 山口さんは日本人ですか Being very generous you could split this sentence into these separate words: 山口　さん　は　日本人　です　か However, this sentence consists of only two phrases: 山口さんは　日本人ですか Where:

  • 山口さんは
    • 山口 - core meaning word (surname)
    • さん - honorific suffix
    • は - particle
  • 日本人ですか
    • 日本人 - core meaning word
    • です - copula
    • か - particle

Therefore the whole sentence would be stressed like this:

やまぐちさんは　にほんじんですか

And not

やまぐち　さん　は　にほんじん　です　か

Stressed mora

It's the last high mora before a downstep. Note that if there's no downstep (heiban), the final mora is not stressed. In this wiki, stressed moras are marked in red. Examples:

  • せんせい (先生) - せ is the last high mora, so it's stressed
  • アニメ - ア is the last high mora, so it's stressed
  • はな (花) - な is the last high mora (the downstep is still there because it's odaka)
  • わたし - no stressed mora (し is the last high mora but there's no downstep after it)

An expression "X is stressed" is equivalent to "X is a stressed mora", and by extension "X is the last high mora and after it there's a downstep"

Stressed word/phrase

It's a phrase which has a stressed mora. In practice, heiban is consider non-stressed and atamadaka, nakadaka, and odaka are considered stressed

Weak mora

It's a mora which cannot be stressed, even if it otherwise would following the regular rules. っ and ん are never stressed and therefore are considered weak. Additionaly, for some long vowels/glides the second mora is considered weak, but it's not always the case. Examples:

  • せんせい (先生) - ん and い are weak moras
  • おおい (多い) - the second お is a weak mora as it's the second mora in the long o
  • かえる (帰る) - え is a weak mora as it's the second mora of the ae glide

In almost every case, when a weak mora needs to be stressed, the stress moves one mora back:

  • しゃかいじん (社会人) not しゃかいじん, because い is a weak mora. There are more details in the suffixes section

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