If you’ve studied Japanese for a little time or a long time, you’ve probably run across rendaku. You might not know what it is, just based off the name, but surely it’s confused you once or twice. Rendaku means “sequential voicing” – to put things more simply, these are the words that either repeat (ひとびと) or consist of a couple words put together (てがみ) where the second word/piece’s first kana either gets modified with dakuten or it doesn’t. Most people will go their entire Japanese studying lives just memorizing these rendaku words, but did you know there’s a way to know when the second word gets modified and when it doesn’t? Prepare for super-duper technical stuff, coming up (don’t worry, I’ll try to make it super-duper simplified where I can!).

[box type=”tick”]To get the most out of this post, you’ll need to know hiragana. Want to learn hiragana and get started learning Japanese? Go through TextFugu’s hiragana chapters for free, and get started (I think you’ll be surprised how much you’ll be able to learn).[/box]

Some Examples Of Rendaku Words:

I think the first thing to do is take a look at some words that have this behavior – it’s much easier to see what I mean than anything else, I think. That way you’ll have a base to work off of when we get into the nitty-gritty of explaining why and when it happens.

さくら turns to ざくら

かっぱ turns to がっぱ

はな turns to ばな

ひと turns to びと

とき turns to どき

かいしゃ changes to がいしゃ

See how the first kana in the second section / word changes to its dakuten counter part (that’s when you add the ” to it to change its sound). These are all examples of rendaku words. Now let’s look at some you’d think are rendaku words, but aren’t.

What Doesn’t Cause Rendaku?

That’s the question we should be asking rather than “what does cause rendaku?” Why? Simply because there are more solid rules around this than the other way around. Also, this will allow us to categorize the combo-nouns in a way that lets us examine them more effectively. And, let me warn you. Things are about to get crazy…

1. Already Has a Dakuten/Dakuon

If the second word already has a dakuten then there’s nothing you can do to make it go rendaku. If the dakuten is there in the second word/section, then the dakuten stays. There’s no anti-rendaku or anything like that which will take it away.

2. Lyman’s Law

Lyman’s law is perhaps the most famous way to figure out whether or not a word will get the rendaku treatment or not. Lyman’s law states that:

Rendaku does not occur when the second element of the compound contains a voiced obstruent in any position.

First off, we should probably define what a voiced obstruent is (seriously, wth linguistic people?). A voiced obstruent, put simply, it is a consonant sound (so, not a vowel) which is formed by obstructing airflow in your throat. It took me a while to figure this out, but if you do a lot of these sounds slowly, you’ll find your throat has to close a bit (and obstruct airflow) in order to be made. “Voiced Obstruent” sounds are b, d, g, v, j, and z (which make a vibration in your throat, too, if you want try it out!). Of course, not all of these or applicable. The voiced obstruents “B” and “G” for example would mean the kana is already in dakuon/dakuten status, meaning (according to the first point) they’d never go rendaku status. Also, “V” doesn’t exist in Japanese sounds.

That being said, though, there are exceptions to this “law” but it’ll keep you in the clear most of the time.

Anyways, the idea is basically this: Rendaku won’t occur as much when the second word/section has a voiced obstruent in it. Let’s take a look at some examples:

人々(ひとびと)= People
The second section (the びと, originally ひと) has no voiced obstruent in it. When it has a voiced obstruent, the rendaku won’t occur. Because it didn’t have a voiced obstruent in it, it does get the rendaku treatment. b, d, g, v, j, and z.

時々(ときどき)= Sometimes
This has no voiced obstruents in it, so it goes rendaku.

山火事(やまかじ)= Forest Fire
The second word/section (かじ) does contain a voiced obstruent. Therefor, rendaku does not occur (it is やまかじ not やまがじ).

There are exceptions and rendaku has continued to be one of those things that’s hard to pin down perfectly (sounds like the entire Japanese language, right?). Beyond Lyman’s law (which is probably the safest bet) there are other things you can do as well to help you on your rendaku quest.

3. Foreign Words

Another thing you can add to your rendaku knowledge-base arsenal is the behavior of foreign words. There are two pieces to this, so let’s start with the easiest one first (non-Chinese foreign words).

Japanese has a lot of loan words, where non-Japanese words have been added to the language. These are usually written in katakana. In cases like this, you’ll hardly ever see rendaku being used:

As you can see, it’s not アイスゴーヒー (also following Lyman’s Law, on top of this)

Beyond this, though, there’s another class of (less) foreign words. These are words imported via kanji. Kanji has both the on’yomi and the kun’yomi readings. The on’yomi reading are the “Chinese” readings of the kanji. A lot of words consist of two or more kanji combined together to make a word. These jukugo (combo-kanji) are also rarely get the rendaku treatment, though it definitely does happen (at least more often than really foreign words). Still, overall native (kun’yomi) Japanese words tend to be more prone to rendaku than Sino-Japanese (words of Chinese origin… on’yomi readings) words. That being said – never trust any Chinese words, they’re tricky (was that racist? I’m not sure…).

Groups Of Rendaku Behavior

Lyman’s law and other “behavior rules” aren’t always reliable. There are some other things you can do to help figure out when rendaku takes place or doesn’t take place. There are different “groups” of words that have different kinds of rules – if you know these groups (especially the first one) you’ll be able to figure figure out rendaku words more effectively.

1. Never Go Rendaku (Immune)

This set of Japanese (“Yamato”) nouns (versus nouns imported from China … we’re talking kun’yomi here) never undergo the rendaku treatment. Out of allllll the Japanese word nouns out there, this is a tiny fraction. It’s the exception so to speak, but it’s also solid, without any exceptions of its own.

  • 浜(はま)= Beach
  • 下(した)= Below
  • 土(つち)= Earth
  • はし(はし)= Edge
  • かまち(かまち)= Framework
  • 滓(かす)= Garbage, Scum
  • 艶(つや)= Gloss
  • 枷(かせ)= Handcuffs
  • 暇(ひま)= Leisure
  • 北(きた)= North
  • 姫(ひめ)= Princess
  • 形(かたち)= Shape
  • 煙(けむり)= Smoke
  • 紐(ひも)= String

So, with these examples, you can conclude that none of them will appear in the rendaku form (ひま will never be びま, けむり will never be げむり, and so on). Want some examples of this? Here you go:

横浜(よこはま)= Yokohama (the city)
よこはま doesn’t turn to よこばま
As far as I can tell, this doesn’t have a voiced obstruent in the はま, but because it’s one of the exception words it doesn’t change to ばま.

顔形(かおかたち)= Facial Features
かたち stays at かたち. It is immune to rendaku.

血煙(ちけむり)= Squirt Of Blood
けむり stays at けむり, just like it should.

You can also do a search on where you take the word (above) and put a * before it. That will show you all the words with something before the word you put in. For example, if you put in *暇 you’ll get all the words with stuff before 暇 in them. You’ll have to look for the ones that are pronounced ひま though, rather than the on’yomi or other pronunciations.

Example: Look up *暇

If you learn this group of words (and you will eventually, though it’ll happen automagically over time as you gain more experience), you’ll at least know a list of words that never get the rendaku treatment. There are others, as well, though, and they’re not quite as friendly.

Then again, just like with everything rendaku, there’s exceptions with the “never go rendaku” words too. Not so “never go rendaku” are you, rendaku? Just shows why this topic is so difficult to pin down.

2. Rendaku Resistors

The above Group never gets all rendaku up in your face. This group of nouns just resists the rendaku treatment, where it is the exception when it happens.

According to a study done by Eric Rosen (“Systematic Irregularity in Japanese Rendaku: How the grammar mediates patterned lexical exceptions” … seriously, a mouthful of a title), these 8 nouns consist of 50% of all the cases of rendaku resisting words. That means if study these eight words and the combo-words they’re involved in, you can make educated guesses on some of the words you’re not sure about when you see them written in kanji.

  • 草(くさ)= Grass → Resists rendaku 84% of the time
  • 原(はら)= Field → Resists 57%
  • 癖(くせ)= Habit→ Resists 75%
  • 皮(かわ)= Skin → Resists 42%
  • 先(さき)= Tip → Resists 100%
  • 木(き)= Tree → Resists 61%
  • 子(こ)= Child → Resists 38%
  • 手(て)= Hand → Resists 75%

Now, there’s something interesting about the rendaku resisters. Their resistance occurs only in “short-short” compounds. That is, compounds that are two or less kana long (on both sides). When there is a long compound, these “rendaku resistant” words can no longer resist. For example:

常盤木(ときわぎ)= ときわ + ぎ
You can see the first compound is three kana long. Thus, it is a “long-short” compound. Anything that’s not a short-short compound will not resist rendaku (if it is a rendaku resisting word).

But, when 木 is used in a short-short compound, things are totally different. Even though it doesn’t resist all the time, the percentage is much better (i.e. not 100% rate of rendaku like long compounds).

丸木(まるき)= Log
This is a short-short compound

本木(もとき)= Original Tree Trunk
もとき is a short-short compound (both sides are two or less kana long), and it is more resistnat.

生木(なまき)= Live Tree
Also resistant.

That being said, there are still short-short compounds for the rendaku resisting words that still can’t resist. It’s just that they don’t occur as often (though they still do occur).

山木(やまぎ)= Mountain Trees
Even though it’s a short-short compound, it can’t resist the rendaku (き becomes ぎ). There are exceptions, since it’s only rendaku resistant and not immune.

I’d say the most tricky ones are the resistant words. They tend to not go rendaku (if you had to bet, you’d at least have better than 50% odds most of the time, I suppose?) but they sometimes do as well. It’s a tricky business, but not something that’s too hard once you’ve studied Japanese for a while and you know a decent number of words.

3. Rendaku Lovers

Then, there’s a group of nouns that love rendaku. They never resist, and you’ll almost always see them in the rendaku form if they are the second part of the word. This is Rosen’s short list of of words that make up 39% of all the occurances of these rendaku loving nouns.

  • 風呂(ふろ)= Bath → 100% Rendaku’d
  • 腹(はら)= Belly → 100% Rendaku’d
  • 船(ふね)= Boat → 100% Rendaku’d
  • 骨(ほね)= Bone → 100% Rendaku’d
  • 花(はな)= Flower → 100% Rendaku’d
  • 笛(ふえ)= Flute → 100% Rendaku’d
  • 金(かね)= Gold → 100% Rendaku’d
  • 口(くち)= Mouth → 100% Rendaku’d
  • 底(そこ)= Bottom/Sole → 100% Rendaku’d
  • 箱(はこ)= Box → 100% Rendaku’d
  • 紙(かみ)= Paper → 100% Rendaku’d
  • 人(ひと)= Person → 100% Rendaku’d
  • 形(かた)= Shape → 100% Rendaku’d

Then, these ones are still Rendaku Lovers, but they don’t love rendaku quite as much as the previous list.

  • 鳥(とり)= Bird → 80% Rendaku’d
  • 雲(くも)= Cloud → 80% Rendaku’d
  • 川(かわ)= River → 61% Rendaku’d
  • 玉(たま)= Ball → 80% Rendaku’d

These words tend to be a little bit more reliable (at least compared to the rendaku resistors). Most of them are 100%, and the ones that aren’t 100% tend to be a lot closer (80% for all but one). If you take a look at these words, they should voice the rendaku every (or almost every) time.

戸口(とぐち)= Doorway

入り口(いりぐち)= Entrance

That being said, I found some exceptions to these rules (as in, some of the 100% ones aren’t 100%). There’s 悪口 (わるくち, which to be fair can also be written わるぐち) and there’s 仕口 (しくち, which isn’t a super common word, but you get my drift). There are others as well, but I think Rosen’s 100% list is pretty close, though I’d bring some of them down to around 90% (still close enough to make smart bets in my book).

Then Again, You Could Just Learn The Words

This is a huge amount of information. I never knew any of this until just recently and somehow got by just fine. I also doubt that anyone else learns about this either, and they somehow get by okay too. I think the above information is helpful, don’t get me wrong, but I think it’s more helpful for making guesses when you aren’t sure how to read a word written out in kanji. With tools like rikaichan (not to mention regular old dictionaries) needing to be able to guess isn’t as necessary as it may have once been.

Still, I think this kind of thing is pretty fascinating. I thought it was all totally random. The Japanese Language Gods were punishing everyone learning Japanese, I thought. I mean, half the Japanese language seems random anyways, so why not this (actually, I think most of the Japanese language makes sense, once you take the time to look at more of the linguistic elements of it).

Most students of Japanese will probably never learn any of this, though – so if you’re learning Japanese, and you made it through this epic post, thumbs up to you. You know more than 99.9% of all Japanese students out there. You could even show off some of your new found crazy linguistic knowledge to your Japanese teacher, too, but I doubt they’ll have any idea what you’re talking about.

Oh, and almost everything above has exceptions (damn you, Japanese Language Gods! *shakes fist at the sky, screams a bit*). Sorry about that :P

P.S. Wish this post was 140 characters instead of 2200 words? You should have followed us on Twitter.

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  • Ollie Capehorn

    Fantastic post. Before this I genuinely had only considered learning the words which feature rendaku rather than thinking it through a bit more. Thanks :) 

  • Evan Ross

    The reason you’re getting so many “exceptions” to Lyman’s law is because you’ve defined “voiced obstruent” incorrectly. p, t, k, f and s are all voiceless obstruents. Voicing is when you can feel your vocal cords vibrating. “Hito” has no voiced obstruent, so that’s why it voices to “bito” in compounds. “Kaji” has a voiced obstruent, but it’s “j” in the second syllable, not “k”. Hope this helps! Please edits your blog post so people don’t get confused!

  • Breana Clark

    This is amazing!  Thank you so much!  <3
    I knew what rendaku was (of course), but I never really could figure out when it applied.. so, the only thing I did was try to take note (and memorize) when I came across it…  but, now, I can figure it out much more effectively!

    Koichi, every one of your posts improves my life, it seems!  (or, at least vastly improves my Japanese-leaning ability.  Same thing!  lol).  You totally rock my socks, you hoopy frood!

  • koichi

    that is suuuper helpful, thanks so much! I was having trouble figuring out what made up the voiced obstruents, and apprently the source where I finally found them defined led me astray (or I didn’t understand all the other fancy linguistic terms in the papers / articles on obstruents I found). Thanks so much – totally makes things easier and clearer now! :D

  • koichi

    that is suuuper helpful, thanks so much! I was having trouble figuring out what made up the voiced obstruents, and apprently the source where I finally found them defined led me astray (or I didn’t understand all the other fancy linguistic terms in the papers / articles on obstruents I found). Thanks so much – totally makes things easier and clearer now! :D

  • Tiffany Harvey

    Thank you so much for the * tip on jisho! I’ve often wanted to look up a kanji that way & thought it couldn’t be done.

  • Matthew Olson

    Seeing this, I am reminded how much I love Japanese linguistics! I learned this last year but it didn’t really stick, so I’m hoping that this post can set me straight.
    Hope to see more great posts like this!

  • koichi

    oh good! Yeah, that one is really helpful sometimes.

  • koichi

    hehe, glad it improves your life! That’s what we try to do each post, if we can :D

  • koichi

    haha, writing this reminded me how much I dislike reading about linguistics :/ I wish linguists didn’t use such fancy words – they’re basically saying “no non-linguists beyond this point” when you start reading one of their papers :(

  • koichi

    haha, not sure it’ll help much :/ I feel like the time that you could put in learning about rendaku could be put into just memorizing the words and patterns, but at least it’s interesting, maybe!

  • Callisto

    Pretty fascinating read, thanks for taking the time to write it out. I had started to get a hang of this, or so I thought. Then when I thought “Ha, I got this. Check it out,” I was completely wrong. Now I know why!

    Also, new comment system? Hmmm. It makes it a little difficult at a glance to know who’s replying to what.

  • Callisto

    Weird the comment system wasn’t loading Disqus for a minute. Good thing I cntrl+a, cntrl+c everything I write, ever.

    Pretty fascinating read, thanks for taking the time to write it out. I had started to get a hang of this, or so I thought. Then when I thought “Ha, I got this. Check it out,” I was completely wrong. Now I know why!

  • Austn3

    Obama the city (小浜 – おばま) is one where 浜 (はま) changes.

  • koichi

    lol, that it is. Time to add more “and yet, there are exceptions” to that part too now :D

  • koichi

    haha, you and I both… I’m so OCD about ctrl+a ctrl+c ctrl+s constantly :/

    And yeah, I think I ended up getting more confused by this subject the more I read about it… I think you have to be some kind of linguistic genius to wrap your head perfectly around everything… or at least that’s what I tell myself :(

  • Brandon Murray

    Mind = Blown. Think I’ll take a nap now.



  • Luciano Tsiros

    I had a general idea about this but never had the chance to go through all of it. Now I took the time to read it thanks to it being on Tofugu. Thanks!

  • Evan Ross

    No problem! :) Keep up the awesome work! ^_^

  • Anonymous

    Here is two other tips:
    Putting a “*” in your search finds items where there are 1 or more characters plus the characters already in your search box, whichever side it’s on. So Putting a “*” in front 木 for example, will find words from two characters like: 青木 to many characters like: アラビアコーヒーの木, and if you want to search for words that begin with 木, just put “*” after it. 

    The “*” is awesome for finding words kanji are in, but you might just want to figure out 1 character that is missing in a word. You might be missing a character at the end or beginning of a word, or in the middle of the word but you know it is only 1 character. To cut out all the longer words, put “?” wherever the missing character would go and it will only look for words where the character or characters in your search as well as that one space exist. You can also use this to find several characters. I put “?木?” in the search box on Jisho and I found 植木屋. I then put “?木??” and found 枯木死灰. If you put “?木?灰” you would also find that. 

    Hope that helps! :)

  • Nihonnikonni

    Awesome post! Thanks for blowing my head during lunch break… I still feel like learning the words with the reading they have to them might be easier than trying to fully understand the concepts you explained. And then there’s this awesome feeling for the right use of a language that you develop at a certain stage in the learning process – the moment where you instinctively make the right use of grammar, vocab or crazy stuff like rendaku. Or is it just me?

    Apart from the not-at-all obvious glitch that Evan Ross pointed out, I think I found a Freudian typo: in the section where you use 時々 as an example (near the end of chapter 2) you used “rakuten” instead of “rendaku”. Either that or it’s some kind of joke I didn’t get. If so, please disregard.

    Other than that: Moar of that! I can’t deny I enjoy getting my brain melted ever now and then.
    (Oh, and I totally Ctrl+A, Ctrl+C everything!)

  • Nihonnikonni

    It’s “molten”, isn’t it…? Sorry! (Talking about irregular grammar…)

  • koichi

    oh my’s I had too much dakuten and rendaku on the mind, they’ve melded into a single horrible new grammar point that nobody knew existed! D: D:

    Thanks for catching that!

  • koichi

    oh my’s I had too much dakuten and rendaku on the mind, they’ve melded into a single horrible new grammar point that nobody knew existed! D: D:

    Thanks for catching that!

  • nagz

    most helpful! thanks

  • Irene

    課す(かす)= Garbage, Scum? I think you’ve got the wrong kanji here… If you’re not trying te be sarcastic. I learned that this kasu means:  to assign a task to~ Like giving students homework and stuff…

  • Uniko

    “Adzuchi” (安土 - あづち, the town in Shiga prefecture which is famous for the Adzuchi Castle,  constructed by Nobunaga Oda) is also an exception.

    And we say “はしばし”(端々) which means “end to end” too.

  • Uniko

    “Adzuchi” (安土 - あづち, the town in Shiga prefecture which is famous for the Adzuchi Castle,  constructed by Nobunaga Oda) is also an exception.And we say “はしばし”(端々) which means “end to end” too.

  • Anonymous

    Whoa! This is one of those things I wondered about, a lot. Thanks for clearing it up with this post. The post itself might not make complete sense to me, yet, but at least now I know why this happens and it clears up some confusion.

    ~ fv

  • Anonymous

    Oh, I see… I actually just posted/replied to the matter of “かじ.” Your explanation cleared that up for me… it did confuse me a little, then I scrolled down, read your post, and said “Oooooh.” All in that order.

  • Anonymous

    Oh, I see… I actually just posted/replied to the matter of “かじ.” Your explanation cleared that up for me… it did confuse me a little, then I scrolled down, read your post, and said “Oooooh.” All in that order.

  • koichi

    derp derp, yep wrong kanji – should have been: 滓

  • koichi

    whoops, j is one too, just added that to the list.

  • koichi

    hrrmm ~ I wonder if names are more prone to exceptions?

  • Tiffany Harvey

    The ? thing will definitely help when I am trying to translate something & the kanji is too small for me to figure out. Thanks!

  • Anonymous

    Awesome, thanks for that. Evan’s post also helped to clear that up.


  • Skurt

    I think my head borked :o

  • Anonymous

    Your Welcome! :)

  • Anonymous

    9 years of formal Japanese language and no one ever mentioned this subject… probably because it’s too confusing but it’s still very useful. I never really understood why all these words where going weird on me one sometimes but it’s great to finally know why they do this.
    Great post, these are the kind of ones I love!!

  • Ashley Galyen

    Interesting about the percentage of times a word turns rendaku.

    I think it would be more helpful to also see a frequency of use percentage for the word compounds.
    There might be a word than turns rendaku 66% of the time, with 3 compounds. But the 1 compound used 90% of the time in daily speech doesn’t use rendaku.

    Wikipedia has an interesting article on this as well with some other key points such as:

    Rendaku also tends not to manifest itself in compounds which have the semantic value of “X and Y” (so-called dvandva or copulative compounds):

    [yama] + [kawa] > [yamakawa] “mountains and rivers”

    Compare this to [yama] + [kawa] > [yamagawa] “mountain river”.

    If this is the case then,

    横浜(よこはま) = yokohama = side-by-side beaches.


     よこばま = yokobama =  side-by-side beach (singular)

    makes no sense which leaves you to play with other meanings of yoko that doesn’t quite make sense either.

    This leads me to believe that the semantics of the first word might also be involved in that percent where words don’t go rendaku. Also broadens my understanding of Japanese place names. It seems like they do have a plural other than adding a suffix to a group of people.

  • j3ss4ndr4

    Maybe I’m just weird, but I love this kind of stuff. ^_^   Got here from the 川 kanji page on Textfugu… quite the side-trip, lol!