The Suffix -Ka 接尾辞の「~化」

第200課: The Suffix ~化: “-ation”

The English suffix “-ation” is a combination of “-ate” and “-ion” used to form nouns which indicate the result of an action or process. Words resulting from this such as “combination,” “sedimentation,” “popularization,” etc. are heavily used in both spoken and written English.

By defining the suffix “-ation,” you can actually make very accurate parallels with its Japanese counterpart. For instance, in English “-ation,” including “-ation” itself, are Latin-based. In Japanese, the corresponding suffix ~化 is Sino-Japanese in origin, and although it is not limited to Sino-Japanese vocabulary, it is predominantly used with said words. 

The Basic Meaning of ~化: 「~になる・~にする」相当の用法

~化 is a powerhouse in creating technical words. When combined with する, it creates thousands of new verbs. Although it is still common in the spoken language, many examples may be more easily phrased with a simpler phrase. 

The verbs created with ~化する provide a layer of nuancing that catches the eye differently than the possible paraphrases ~になる and ~にする. To exemplify this, let’s look at 長期化する (to prolong) and 映画化する (to cinemize).  

1. 長期出張と一口にいっても、どのくらいの期間から長期になるのかわからない人も多いでしょう。
Even when simply stating it as a “long-term business trip,” many people don’t know how long a duration a (trip) would be for it to become ‘long-term.”

2. 失業期間が長期化する前に就職促進を進めていくことが重要だ。
It’s important to advance the promotion of finding employment before the unemployment period becomes prolonged.

3. 何故通常と比較してここまで治療期間が長くなるのかを理解してもらえないことが多い。
It’s often the case that one is unable to have (the individual) comprehend why (their) recovery time has become so long compared to what it would usually be. 

Although it may seem overkill to make this three-way distinction, it must be pointed out that English exhibits the same degree of word variation. “Prolong” is certainly more distinct than “to become longer,” and “to become long-term” could be viewed as an in-between those nuances. 

4. 本を映画にしたものはいろいろ内容が足りないと感じませんか?
Don’t you feel that whenever something goes from book to movie that it’s thoroughly lacking?

5. 映画化した本を読書感想文にしたら先生に怒られると思う?
Do you think the teacher would get mad if you used a cinemized book for a book report?

Learning whether a ~化する is intransitive (~になる), transitive (~にする), or both is no easy task. Seeing how the phrase might be paraphrased is a good diagnostic tool, along with checking for what particles are used. If you see the particle が used, you can assume it’s intransitive. If you see the particle を used, it’ll be transitive. However, it’ll be the verbs that can be either or depending on context that will pose a greater struggle.

※Words made with ~化 start out as nouns before する is attached. For the majority of this lesson, we will be studying the grammar surrounding their verbal rendition. Once that has been covered, we’ll return to how they can be used just like regular nouns.

~化する Transitivity  「~化する」の自他体系

With exception to three basic verbs–開(ひら)く (to open), 閉じる (to close), and 増す (to increase)–verbs of native origin are either solely intransitive or solely transitive–excluding instances where more modern switching has occurred–ex. intr. 終わる in 授業を終わる (to end class). 

Contrary to this, Sino-Japanese vocabulary does not exhibit distinct morphology for intransitive-transitive forms. As a consequence, when those words combine with ~化, it’s not readily obvious how they should be interpreted without seeing how the word is used. For comparison and contrast, let’s take a close look at three verbs. 

Intransitive Transitive Dual Transitivity
To deteriorate
 映画化するTo cinemize 機械化するTo mechanize

If we strip away する, allowing us to look at the standalone nouns, and then translate them back into English, we get “deterioration,” “cinemization,” and “mechanization” respectively. 

Firstly, let’s look at 老朽化する. Although “deteriorate” can be used as a dual transitivity verb in English, the Japanese equivalent cannot. This is likely due to 老朽する, its 化-less verb form is solely intransitive. As for the nuance difference between 老朽する and 老朽化する, the former describes the natural process of something becoming old and losing its utility, and the latter describes a systematic process in which something is aging with the problem being viewed as a problem to contend with. It is possible, however, to turn these expressions into transitive verbs. To do so, we must use the causative form. Thus, whenever a ~化 expression is naturally intransitive, the causative form is necessary to ‘make’ it transitive. Consequently, 老朽化させること would be “the act of letting (something) fall into a state of deterioration.” 

6. 施設維持を怠慢して、老朽化させたように見受けられる。
It is assumed from appearance that (they) have caused it to deteriorate by neglecting facility maintenance.

7. 老朽化した橋が多くある。
There are many deteriorating bridges.

Next, we have 映画化する. This expression is synonymous with 映画にする. In a way, ~化 can be viewed as a fancier alternative to using the particle に. This verb is transitive in nature. To make it intransitive in nature, the passive form would have to be used. Thus, in English we would get “to be cinemized,” and in Japanese, we would get 映画化される.  The conclusion from this is that whenever a ~化 expression is naturally transitive, the passive form is necessary for it to ‘become’ intransitive.

8. 人気の小説を映画化した作品は安定の面白さがある。
Works made by cinemizing popular novels have a steady level of interest.

9. 最新の映画化された小説を読んでみよう。
Let’s read the latest novel to be cinemized.

What’s far more common in Japanese are expressions that can be either transitive or intransitive depending on the context. To determine the transitivity intended, we will need to look out for the particle が for the intransitive sense and the particle を for the transitive sense. In English, “-ize” results in a transitive verb, and to return it to an intransitive state, the passive form is necessary. In Japanese, though, these dual transitive expressions don’t necessitate the passive and causative forms by default, both those forms do exist nonetheless to serve their original purposes. To visualize these four scenarios, consider the following examples with 機械化する.

10. 人間の身体を一部機械化しても人間ですよね?
Even if you turn part of the human body into machine, that’s still a person, right?

11. 人間が機械化した世界が来るとしたら、その先に何があるのか?
If a world in which mankind were to become machines came about, what would that future hold?

12. 1960年代の中ごろから機械化がどんどん進み、1980年代以降、ようやく農作業が完全に機械化された。 
Mechanization began in the mid-1960s and gradually progressed, then from the 1980s onward, farm work at long last was entirely mechanized.

13. 強制的な機械化を推し進める宇宙人は、その惑星の住民たちを逮捕し、次々と機械化させた。
Aliens forging ahead with compulsive mechanization arrested the residents of that planet and forced them to become machines one after another.

Japanese verbs when viewed in totality hardly ever exhibit dual transitivity. With a few exceptional verbs such as 開(ひら)く (to open) and 増す (to increase), most verbs are either solely intransitive or solely transitive, and if semantically reasonable, they may have an alternative form for the other role. ~化 verbs appear quite exceptional to this rule of thumb. The overwhelming majority of them exhibit this dual transitivity. 

As for why the passive and causative form still exist for these verbs should be apparent from the previous examples. The passive form implies that there was an agent (doer) which sought the process described. Agriculture doesn’t mechanize by itself. People are ultimately responsible. However, in Ex. 11 where we see 機械化する used as a standalone intransitive verb, the meaning is identical “to become machines.” Although becoming a machine would necessitate a willful process, the emphasis is on “becoming that state.” Similarly, if mechanization is forced upon someone, that necessitates the use of the causative form to highlight that coercion.

50/50 Intransitive-Transitive Examples  自他拮抗語群

The majority of ~化する verbs lean towards being used as intransitive verbs due to how having mostly entered the language from Sino-Japanese vocabulary. This, however, is a morphological constraint that has not prevented these verbs from taking on transitive contexts. 

In reality, even though intransitive-leaning examples are most common, transitive-leaning contexts are most common. This is because in either situation, positive change tends to cause a speaker to talk about the driving force(s) behind said change. As such, for words that express neutral change, other factors such as the presence or lack of a subject and/or agent (doer) will play a larger role.

14. 全力で社内を活性化してみせる!
I’ll show just how to invigorate the company internally with all I have!

15. いわゆる〝細胞のエネルギー工場″ミトコンドリアを活性化して免疫老化を防ごう!
Prevent aging of your immunity by rejuvenating your mitochondria, the so-called “energy factory of the cell.”

16. 脳が活性化している状態というのは、脳の血流が豊富な状態のことを指す。
“The brain being stimulated” is in reference to the brain’s blood flow being rich.

Unfortunately, because the passive and causative forms play their own specific semantic roles, they are not good indicators as to whether a verb leans towards being intransitive or transitive.

Predominantly Intransitive Examples 自動詞優勢語群

When a word is heavily used in negative contexts, that word is most likely to be used as an intransitive verb. Perfect examples of this are the verbs 弱体化する and 複雑化する. It must be noted that “negative” here is not in reference to negative forms but a context that is viewed in a negative light.

17. 日本経済は、消費増税に耐えられないレベルまで弱体化している。
The Japanese economy has weakened to the point that it cannot withstand the increase in sales tax.

18. 課題もニーズも複雑化するなかで、「AI」をどう活用すべきか?
As issues and needs become ever more complicated, how should one utilize “AI”?

Nonetheless, verbs that are usually intransitive are still frequently used in positive contexts. In fact, these situations are far more common overall. The point being made is that sentences utilizing the transitive usage for a negative change is far less common than with the intransitive usage. 


19. 福井県で養殖されているカキの出荷が本格化している。
The shipment of oysters being cultivated in Fukui Prefecture is proceeding at full speed.

20. 新幹線の車両はアルミニウム車体が一般化している。

Cars made of aluminum are used in general for bullet train cars. 

21. アメリカでは屋内は原則として禁煙だが、屋外では路上喫煙が可能で、さらに悪いことには路上喫煙をした後の吸い殻のポイ捨てが一般化している。
In America, spoken indoors is prohibited in principle; however, as for outdoors, smoking on the streets is possible, and what’s worse, the littering of cigarette buds after smoking on the streets is normalized.

Predominantly Transitive Examples 他動詞優勢語群

~化する that are said to be predominantly used as transitive verbs are heavily used when the change is deemed positive. There is also a more active role of the agent of that change as a result. Although it is by no means ungrammatical to use these verbs to describe negative change, this is not as common. 

22. 君は自分を正当化しているだけだ。
You’re just justifying yourself.

23. 仕事を効率化しても、仕事の量は減らない。
Even if you optimize work, work load will not decrease.

24. ヨルダンがイスラエルと国交を正常化したのはいつだったでしょうか。

When was it that Jordan normalized diplomatic relations with Israel?

Using ~化 with Any Word Origin 漢語・和語・外来語+~化

Although the positive-negative perception of the change described by ~化 plays some role in determining the transitivity of the verb, it is still necessary that you expose yourself to lots of examples of a given word to determine how it can be used. Intransitive-transitive usages are usually marked distinctly in Japanese dictionaries, which can save you time if you are wondering if one way or the other is at least possible.

Having tackled transitivity to a degree, though, it is time to move onto seeing more examples of the suffix in general. In doing so, we’ll not only look at lots of Sino-Japanese examples but also the not-so-rare examples made from loanwords as well as native vocabulary.

漢語+化 漢語+化 外来語+化 和語+化
液化Liquefaction 浄化Purification グローバル化 Globalization 畑化Turning into field(s)
 高齢化Population aging 劣化Degradation カプセル化Encapsulation 大型化Increasing in size
 風化Weathering 国際化 Internationalization イオン化 Ionization 見える化Visualization
 少子化Declining birth rate 現実化Realization スリム化Streamlining モノ化Objectification
 情報化Computerization 顕在化Actualization  ガラパゴス化Galapagosization ミイラ化 Mummification
 明確化Clarification 近代化Modernization コモディティー化Commoditization オヤジ化Becoming like an old man
 工業化 Industrialization 進化 Evolution オープン化Making available
 国有化 Nationalization 自由化 Liberalization アイコン化Iconization
 激化 Intensification 同化 Assimilation クローン化 Cloning
 合理化 Rationalization 帰化 Naturalization データベース化Making into a database

※Examples with native vocabulary are all very recent neologisms. For instance, 見える化 was actually coined in 1998 by Toyota. It has since become an important jargon in manufacturing/industrial management. 

※畑化 may sound made-up to many speakers as it is overshadowed by the Sino-Japanese equivalent 耕地化.

※Most examples made with loanwords are made by attaching ~化 to nouns, but because the original part of speech will be easily lost upon entering Japanese, this is by no means a requirement as demonstrated by グローバル化. 

※As indicated by how all these words are translated, it’s important not to forget that any ~化 word can function as a standalone noun–see below.

Example Sentences 例文

It’s now time to look at a number of sentences to get a full grasp of how ~化する is used. Important notes on transitivity will be occasionally mentioned; however, because so many verbs are inconclusively one way or another, such labeling cannot be misconstrued as being conclusive. It is always best to first look up the keyword in a dictionary to see if both intransitive and transitive connotations are possible with it. 

25. ITの進化に伴って日常生活のあらゆるものが機械化されてきた。
Following the evolution of IT, all sorts of things of everyday life have become mechanized.

Transitivity Note: The use of 機械化される for the intransitive use of this verb is done when one wishes to implicit hint at the agent. Meaning, in this example, people would have been actively working in the background to bring about the mechanization of everyday things via IT innovation.

26. もし中国が民主化したらチベットやウイグル、内モンゴルは独立するんでしょうか。
If China were to become democratic, would Tibet, Uygur, and Inner Mongolia become independent?

27. 日本は西洋の政治制度や文化を輸入して、(国を)近代化しました。
By importing a Western political system and Western culture, Japan modernized (its country).

28. 自動運転は、完全に50年後に実用化するでしょう。
Automated driving will likely become completely practical fifty years from now.

29. 被子植物は白亜紀以降に急速に多様化しました。
Flowering plants rapidly diversified from the Cretaceous period onward.

30. 時代と共ともに、言葉の使い方や意味(など)が変化します。
The usage and meanings of words change with time.

31. スーパーのウズラの卵には有精卵が混じっていて、ちゃんと温めれば孵化する可能性があります。
Fertilized eggs are mixed with the quail eggs at the supermarket, and when you properly warm them up, there’s the possibility (of one) hatching.

32. ヒトとチンパンジーが種分化したのは500万年から700万年くらい前と言われています。
It is said that humans and chimpanzees speciated from about 5 million to 7 million years ago.

33. 酸化した油は危険です。
Oxidized oil is dangerous.

34. セルロースは短期間で液化した。
The cellulose liquefied in a short period of time.

35. 排水を浄化して再利用しています。
We reuse drainage water by purifying it.

36. 砂は岩石が風化してできた物である。
Sand is what is formed from rocks eroding.

37. 他の民族を同化{する・させる}。
To assimilate other ethnic groups.

Transitivity Note: Using 同化させる implies far more forceful assimilation.

38. 我々は経営体制を強化しました。
We’ve intensified our management structure.

39. 舗装が劣化している歩道を直してほしい。
I’d like the sidewalks with the pavement deteriorating fixed.

40. 人間が草を消化できないのは何故ですか。
Why is it that humans can’t digest grass?

41. 周りの田をそのまま【畑化?・耕地化〇・畑に◎】しても、重粘土質の土壌なら作物の根が窒息して枯れてしまいます。

Even if you just change the rice paddy field into a (regular) field, if the soil is heavy with clay, the roots of your crop will suffocate and die.

42. 内部被曝は悪化するでしょう。
Internal exposure to radiation will likely worsen.

43. インターネット時代には、兵器も情報化しているのです。
In the Internet age, weapons are also being computerized.

44. 学術用語が一般化して意味が広がることが多い。
There are many instances in which technical terms become generalized and expand in meaning.

45. Googleという単語は、一般動詞化している。
The word “Google” has turned into a standard verb.

46. 脳を活性化して勉強べの効率をアップさせましょう。
Increase the efficiency of your studying by stimulating your brain!

47. 水の使い過ぎによって砂漠化しているところもあります。
There are also places that are becoming desert due to the overuse of water.

48. 水道事業が民営化したら水道代は半分になるって本当なんですか。

If the water supply were to privatize, would water bills really go down to half what they are?

49. ネット通販の荷物の増加と人手不足で従業員の長時間労働が深刻化している。
Long-hour labor is becoming more severe due to increases in packages from e-commerce and labor shortages.

50. 東芝の臨時株主総会で、半導体事業を分社化することについて、3分の2以上の株主が賛成して承認された。
At the Special General Meeting of Shareholders, over two thirds of the shareholders supported the splitting off of the semiconductor business, which then (the split-off) was approved.

51. 鹿児島県の奄美大島と徳之島にだけ生息する国の特別天然記念物のアマミノクロウサギが野生化した猫に襲われるケースが相次いでいる。
Cases of the Amamino rabbit, a nationally protected species which only inhabits the islands of Amami Ōshima and Tokunoshima, being attacked by feral cats are happening one after another.

52. 現金をデジタル化しないと現代の決済手段として生き残れない。
If we don’t digitize cash, it won’t be able to last as a modern means of payment.

53. 包装を簡素化し、宣伝費も削減するなどして大手メーカーより安い商品を販売しようとしている。
(They) are trying to market merchandise cheaper than major manufacturers by simplifying packaging, reducing advertising expenses, and other means. 

54. 党執行部では、原発の稼働をゼロにする目標の時期を「2030年」に事実上、前倒しして法案化することを検討していた。
(They) had been considering legislating the goal period of reducing nuclear operations to zero, in actuality, ahead of schedule to 2030 among the executives of the party.

55. サイバー攻撃もますます巧妙化している。
Cyber attacks are also gradually becoming more sophisticated.

~化 as a Noun 「~化」の名詞用法

As has been alluded to throughout this lesson, any ~化 expression is a standalone noun in its own right. In fact, the nominal usage of these words is just as common, and you may also find it easier to avoid using ~化する by following ~化 with some other verb phrase whenever transitivity gets too confusing. 

56. 発注書の発行が自動化したことにより、省力化が進んだ。
By automatizing the issuance of work orders, it made progress in labor savings.

57. 作業は簡単でも頻度の高い運用タスクを自動化した場合、効率化が期待できます。
In the event we automate simple yet high-frequency operation tasks, we can expect our work to be optimized. 

58. 業務の分散化を図っています。
We are considering decentralizing business-work.

59. 再配達の有料化を解決策として挙げる意見も目立った。
Opinions calling for putting forward the charging of redelivering into the solution strategy also stood out.

60. ここ数年は価格競争の激化などで業績は伸び悩んでいる。
In these past several years, performance has been making little progress due to the intensification of price competition.

61. 今回の事故を受けて、栃木県教育委員会は、ビーコンの義務化を検討している。
In response to this incident, the Tochigi Prefecture Board of Education is making it a point to consider the mandating of beacons.

62. 日本維新の会は、去年発表した憲法改正原案に、教育無償化を盛り込んだ。
The Japan Restoration Party incorporated making education free of charge in their original draft for constitutional reform, which they announced last year. 

63. 高齢化や人口の減少が進んでいたところにイノシシによる田畑の被害が相次いだ。

Just as population ageing and population decreasing has progressed, damage to fields by wild boars have occurred one after another.

64. ライバルとの差別化で事業を更に強化することが課題となっている。
Further strengthening business via differentiation from rivals has become the task at hand.


To conclude, it’s also worth noting that 化する is a standalone, intransitive verb with the meaning of “to change.” It is more literary and/or figurative than other synonymous expressions, but it is thanks to this usage that the suffix usage came about.

65. 東京じゅうが、見渡す限り、忽ち焼け野原に化した
All of Tokyo, as far as one could see, instantly transformed into a burnt landscape.

66. 廃墟と化した「軍艦島」はなぜ世界遺産と登録されたのか?
Why is it that “Battleship Island,” which is left in ruins, has been registered as a World Heritage site?