Naru or Suru: Becoming Something Versus Making It So

One question decides the verb

Before you conjugate anything, ask a single question: did this change simply happen, or did somebody make it happen? If the change arrived on its own, through weather, time, growth, prices or circumstance, you want naru. If a person chose it and acted, you want suru. Everything else in the pattern stays the same, which is why these two verbs are usually taught as a pair rather than separately.

The particles follow that split. With naru, the thing that changed is the subject and takes ga or wa: heya ga atatakaku narimashita. With suru, the thing changed is an object and takes o: heya o atatakaku shimashita. If you find yourself unsure which particle to use, you probably have not yet decided which verb you mean, and the particle guide will not rescue you until you do.

How each word type connects

Read the middle two columns as one shape with two endings. Once takaku is formed, both takaku narimasu and takaku shimasu are available, so the work of conjugating is done before you pick a verb. The only form worth drilling separately is ii, whose stem is yo-: yoku narimasu, not the incorrect iku narimasu.

Both verbs are ordinary godan and irregular verbs elsewhere, so all the tenses you already know apply. Naru is a godan verb: narimasu, narimashita, naranai, natte. Suru is the irregular one: shimasu, shimashita, shinai, shite. The te-form guide covers those endings in detail.

Ku naru with i-adjectives

Drop the final i and add ku, then attach narimasu. This is the everyday way to talk about weather, prices, health, ability, and anything that shifts over time. Japanese uses it constantly in small talk, so it is one of the highest-value patterns a beginner can automate. Adding kimashita gives the sense of a change that has been building: samuku natte kimashita, it has been getting colder.

A common learner error is saying atsui desu ni narimashita or atsui narimashita. There is no desu and no i before naru: the adjective becomes an adverb first. Say the pair aloud a few times, atsui, atsuku narimashita, until the ku slot feels obligatory.

Ni naru with na-adjectives and nouns

Na-adjectives and nouns take ni instead of ku, and nothing else changes. This covers life events, roles, ages, states of health and the arrival of skills: jōzu ni narimashita, genki ni narimashita, hatachi ni narimashita. Complimenting someone's progress with Nihongo ga jōzu ni narimashita ne is far more natural than saying you improved it, and it is exactly what a teacher would say.

Nouns of time and quantity work the same way, which gives you a neat way of announcing a schedule change without blaming anyone: kaigi wa san-ji ni narimashita, the meeting has become three o'clock. In business this is heard as a neutral report, not as an excuse, and it is why so many announcements arrive in this shape.

Ku suru and ni suru: the deliberate version

Swap narimasu for shimasu and the sentence names a doer. This is the pattern behind most polite requests about the environment around you: oto o chiisaku shite kudasai, turn the sound down; shizuka ni shite kudasai, please be quiet. Because the adjective is doing the describing, one pattern replaces a whole set of English verbs such as lower, warm, shorten, simplify and tidy.

Watch the object particle. The thing being changed takes o with an i-adjective form, and na-adjectives and nouns behave the same way: heya o kirei ni shimashita. Shizuka ni shite kudasai looks like an exception only because the object, your own behaviour, is left unsaid.

Kore ni shimasu: choosing and settling

With a noun, ni suru also means to settle on something. This is the standard way to place an order, agree a time, pick a meeting room, or choose between options. Kore ni shimasu is what you say pointing at a menu; watashi wa karē ni shimasu tells the table what you have gone for. The plain volitional shimashō turns it into a proposal: jū-ji ni shimashō, let's make it ten.

The staff reply is usually a confirmation, so learn the pair. Expect kashikomarimashita or hai, kōhī o hitotsu desu ne. If you change your mind, yappari kore ni shimasu is entirely normal and needs no apology. The food-ordering post covers the rest of the restaurant script; here the point is that one grammar pattern carries all of it.

Yō ni naru and yō ni suru for verbs

Adjectives take ku or ni, but a verb needs yō ni in between. Dictionary form plus yō ni narimashita means you have reached the point of doing something: hanaseru yō ni narimashita, I have become able to speak. This is the natural way to describe progress in a language, and it is much better than saying jōzu ni narimashita about yourself, which can sound self-congratulatory.

Yō ni shite imasu is the habit version: I make a point of doing it. With a negative verb it becomes yō ni shite imasu on tabenai, meaning I try not to. Compare tabenaku narimashita, which reports that you simply stopped, with tabenai yō ni shite imasu, which says you are deliberately avoiding it. That contrast alone will make your study plans sound adult.

Koto ni suru and koto ni naru

Attach koto to a plain-form verb and the pattern handles decisions. Koto ni shimashita says I decided, and it puts your hand on the choice: ryūgaku suru koto ni shimashita, I decided to study abroad. Koto ni narimashita says it has been decided, and it leaves the decider unnamed. Both are polite; they differ only in where the responsibility sits.

Japanese speakers announce personal news with koto ni narimashita far more often than English speakers would use a passive, including things they chose themselves, such as a marriage or a move. It sounds modest rather than evasive. There is also a fixed use for rules: koto ni natte imasu describes how things are arranged, which is why staff explaining a policy say sō iu kimari ni natte orimasu instead of naming whoever wrote the rule.

Why naru sounds softer at work

Because naru omits the actor, it lets a speaker report bad news without pointing at a person, including themselves. Nōki ga okuremasu names no one; nōki ga okureru koto ni narimashita is softer still, and both are preferred to saying that a named colleague caused the delay. This is not evasion so much as a shared convention that the fact matters more than the culprit, and business Japanese leans on it heavily.

The same instinct produces the service phrasing you hear in shops, such as shinagire ni natte orimasu for out of stock. One caution: a habit of adding ni narimasu to plain statements, as in kochira menyū ni narimasu, is widely criticised as over-polite filler, and a plain kochira ga menyū de gozaimasu is safer. Use naru where something genuinely changed.

Minimal pairs to drill

Say each pair back to back and change only the verb. If you can hear the difference between the room got warm and I warmed the room without translating, the pattern has landed. When you meet a new adjective, add it to this list rather than starting a new one.

Errors worth checking in your own speech

• Leaving i on the adjective: say atsuku narimashita, never atsui narimashita.
• Using ku after a na-adjective: it is shizuka ni narimashita, not shizukaku narimashita.
• Forgetting the irregular ii: the form is yoku narimashita.
• Using ga with suru: the thing you change takes o, as in heya o atatakaku shimashita.
• Dropping yō ni before a verb: hanasu yō ni narimashita, not hanasu narimashita.
• Reaching for a causative when naru would do; ame ga furimashita needs no actor, and neither does most weather talk.
• Overusing ni narimasu as a politeness cushion in service situations, where de gozaimasu is the safer choice.