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.
～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).
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."
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.
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."
It is assumed from appearance that (they) have caused it to deteriorate by neglecting facility maintenance.
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.
Works made by cinemizing popular novels have a steady level of interest.
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.
Even if you turn part of the human body into machine, that's still a person, right?
If a world in which mankind were to become machines came about, what would that future hold?
Mechanization began in the mid-1960s and gradually progressed, then from the 1980s onward, farm work at long last was entirely mechanized.
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.
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.
I'll show just how to invigorate the company internally with all I have!
Prevent aging of your immunity by rejuvenating your mitochondria, the so-called "energy factory of the cell."
"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.
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.
The Japanese economy has weakened to the point that it cannot withstand the increase in sales tax.
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.
The shipment of oysters being cultivated in Fukui Prefecture is proceeding at full speed.
Cars made of aluminum are used in general for bullet train cars.
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.
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.
Turning into field(s)
Increasing in size
Declining birth rate
Becoming like an old man
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.
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.
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.
If China were to become democratic, would Tibet, Uygur, and Inner Mongolia become independent?
By importing a Western political system and Western culture, Japan modernized (its country).
Automated driving will likely become completely practical fifty years from now.
Flowering plants rapidly diversified from the Cretaceous period onward.
The usage and meanings of words change with time.
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.
It is said that humans and chimpanzees speciated from about 5 million to 7 million years ago.
Oxidized oil is dangerous.
The cellulose liquefied in a short period of time.
We reuse drainage water by purifying it.
Sand is what is formed from rocks eroding.
To assimilate other ethnic groups.
Transitivity Note: Using 同化させる implies far more forceful assimilation.
We’ve intensified our management structure.
I’d like the sidewalks with the pavement deteriorating fixed.
Why is it that humans can’t digest grass?
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.
Internal exposure to radiation will likely worsen.
In the Internet age, weapons are also being computerized.
There are many instances in which technical terms become generalized and expand in meaning.
The word “Google” has turned into a standard verb.
Increase the efficiency of your studying by stimulating your brain!
There are also places that are becoming desert due to the overuse of water.
If the water supply were to privatize, would water bills really go down to half what they are?
Long-hour labor is becoming more severe due to increases in packages from e-commerce and labor shortages.
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.
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.
If we don’t digitize cash, it won’t be able to last as a modern means of payment.
(They) are trying to market merchandise cheaper than major manufacturers by simplifying packaging, reducing advertising expenses, and other means.
(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.
Cyber attacks are also gradually becoming more sophisticated.
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.
By automatizing the issuance of work orders, it made progress in labor savings.
In the event we automate simple yet high-frequency operation tasks, we can expect our work to be optimized.
We are considering decentralizing business-work.
Opinions calling for putting forward the charging of redelivering into the solution strategy also stood out.
In these past several years, performance has been making little progress due to the intensification of price competition.
In response to this incident, the Tochigi Prefecture Board of Education is making it a point to consider the mandating of beacons.
The Japan Restoration Party incorporated making education free of charge in their original draft for constitutional reform, which they announced last year.
Just as population ageing and population decreasing has progressed, damage to fields by wild boars have occurred one after another.
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.
All of Tokyo, as far as one could see, instantly transformed into a burnt landscape.
Why is it that "Battleship Island," which is left in ruins, has been registered as a World Heritage site?