Joining words: Who put the g in Shimaguni?

You may have learnt the word for country, 国 KUNI. You may also know the word for island, 島 SHIMA.

When these words come together, the KUNI changes to GUNI. If you are wondering why, please read on.

This word-sound changing phenomenon is called RENDAKU.

Rendaku is when the first consonant of the second word changes from unvoiced to voiced.

The unvoiced consonants that change to voiced consonants are K, S, T and H.

Voiced consonants include G, Z, D and B. They are called voiced because if you make these sounds outloud, you will feel your vocal cords vibrating.

K > Z. S > Z. T > D. H > B.

Example 1: add ORI (fold) to KAMI (paper).

Put them together and you have: ORIGAMI

Example 2: add NEKO (cat) to SUKI (like/love).

Put them together and you have: NEKOZUKI (cat-lover).

Example 3: add INAKA (countryside) to SAMURAI (samurai)

Put them together and you get: INAKAZAMURAI (rural samurai)

Is this starting to make sense?

But before you start rendaku-ing your entire Japanese vocabulary, please note there are many occasions when the sounds do not change.

I will outline the main rendaku rules here with some common examples. (Note there are many exceptions)

For example, Chinese origin words rarely rendaku.

Other foreign origin words almost never rendaku.

Japanese origin words do rendaku, but there are many exceptions.

For example, if the 2nd word already has a voiced sound such as KAZE (wind) or KAJI (fire) there is no rendaku.

NATSU(summer) + KAZE(wind)= NATSUKAZE (summer wind).

YAMA (mountain) + KAJI (fire)= YAMAKAJI (mountain fire)

Also, if the words are pairs with parallel meanings such as SUKIKIRAI (like and dislikes), YAMAKAWA (mountains and rivers), OYAKO (parents and children), they do not RENDAKU.

So, why rendaku in the first place? Two strong theories seem to be firstly that it makes the word easier to pronounce.

Secondly, voicing the start of 2nd word makes it easier to understand when one word starts and the other finishes.

Here is a short quiz:

See if you can answer these 5 examples. The answers at the bottom.

  1. Add DAI (platfrom) to TOKORO (place)
  2. Add AO (blue) to SORA (sky)
  3. Add IRI (entry) to KUCHI (opening)
  4. Add INU (dog) to KIRAI (dislike)


  1. DAIDOKORO (kitchen)
  2. AOZORA (blue sky)
  3. INUGIRAI (dog-hater)
  4. IRIGUCHI (entrance)

Before I leave to you wander off rendaku-ing, I should mention the P sound.

H can change to the half-voiced P sound when the last sound of the 1st word is TSU or N.

For example SHUTSU (go out) + HATSU (start)=SHUPPATSU

EN (lead) + HITSU (writing brush) = ENPITSU

And SAN (3) + FUN (minute)=SANPUN (3 minutes).

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