Reasons and Rules for Pronunciation Changes

Table of Contents

1. Why “がっこう” instead of “がくこう”?
2. Rule ①
3. Rule ②
4. Rule ③
5. Let’s Practice
6. Summary
7. Quiz
8. Similer Articles
9. Comment

Q: Why does “学校がっこう（がっこう）” change from the expected “がくこう” reading? Why does the pronunciation differ from the original kanji readings? Are there any rules?

A: This is due to a uniquely Japanese sound change called 促音そくおん化か, or gemination. In words like “がくこう,” the consecutive consonants make pronunciation difficult for native speakers, so a small “っ” is inserted to make it easier to say—resulting in “がっこう.”
This doesn’t happen in all words, but there are several common patterns. Let’s take a closer look at them next.

Rule ①: Gemination with K-sounds

Let’s start with the example mentioned in the question: “学校がっこう,” and explain how gemination works.

When two kanji are combined into one word and the first ends in a K-sound such as “く (ku)” (as in “学がく”), and the second begins with another K-sound like “こ (ko)” (as in “校こう”), the pronunciation becomes difficult. To make it easier to say, a small “っ” is inserted between them. This is what’s called gemination.

[Examples]
学がく（がく）＋校こう（こう）→ がっこう
学がく（がく）＋級きゅう（きゅう）→ がっきゅう
国くに（こく）＋会かい（かい）→ こっかい
国くに（こく）＋境きょう（きょう）→ こっきょう
石いし（せき）＋器き（き）→ せっき

As seen above, when the first word ends in a K-sound like “く” or “き” and the second word also starts with a K-sound, gemination commonly occurs with the insertion of “っ.”

Rule ②: Gemination with words ending in “き,” “ち,” or “つ” + starting with K-, S-, or T-sounds

When two kanji are combined and the first ends in a sound like “き,” “ち,” or “つ” and the second begins with a consonant from the K-, S-, or T-line, a small “っ” is often inserted to smooth the pronunciation. This is another common pattern of sokuonka (gemination).

[Examples]
匹ひき（ひき）＋敵てき（てき） → ひってき
一いち（いち）＋滴てき（てき） → いってき
一いち（いち）＋生しょう（しょう） → いっしょう
決けつ（けつ）＋心しん（しん） → けっしん
結けつ（けつ）＋婚こん（こん） → けっこん

As shown above, when a word ends in “ki,” “chi,” or “tsu” and is followed by a word starting with K-, S-, or T-sounds, gemination tends to occur.

Rule ③: When “じゅう” (ten) is followed by K-, S-, T-, or H-sounds

When the number word “じゅう” (ten) comes at the beginning of a compound and is followed by a word starting with a K-, S-, T-, or H/P-sound, the pronunciation often changes to a “じゅっ〜” form to make it easier to say. This is also a type of gemination.

[Examples]
十じゅう（じゅう）＋回かい（かい） → じゅっかい
十じゅう（じゅう）＋冊さつ（さつ） → じゅっさつ
十じゅう（じゅう）＋着き（ちゃく） → じゅっちゃく
十じゅう（じゅう）＋分ぶん（ぷん） → じゅっぷん

As seen here, gemination commonly occurs not only in kanji compounds but also in number-based expressions.

Let’s Practice

Based on the rules so far, try to figure out how the following compound words are pronounced:

① 作さく（さく）＋家か（か）
② 出しゅつ（しゅつ）＋勤きん（きん）
③ 十じゅう（じゅう）＋匹ひき（ぴき）
④ 積せき（せき）＋極きょく（きょく）

How would you read them? Think it through first, then check your answers below.

[Answers]
① 作家さっか
② 出勤しゅっきん
③ 十じゅっ匹ぴき
④ 積極せっきょく

Summary

• In Japanese, when similar consonants occur in succession, they can be difficult to pronounce. To make pronunciation smoother, a small “っ” (called sokuon) is often inserted. This phenomenon is known as 促音そくおん化か, or gemination.
• Here are the main rules:
  ● Gemination caused by consecutive K sounds
  When the first word ends in “ku” and the second begins with “ko” or another K-sound, a small “っ” is commonly inserted.
  
  ● Words ending in “ki,” “chi,” or “tsu” + words starting with K-, S-, or T-sounds
  When the first word ends with one of these sounds and the second begins with a K, S, or T consonant, gemination often occurs.
  
  ● “Jū” (十じゅう) + words starting with K-, S-, T-, or H/P-sounds
  When the number “jū” (ten) is followed by a word starting with one of these consonants, the pronunciation changes to “jup-,” “jus-,” etc.

Quiz

How do you read the following words?
Think about whether gemination occurs or not.

Click on the question to check the answer.

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Similer Articles

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