Japanese Grammar: Make Action with
~くします/~にします -
Intermediate Lessons: 31

In this lesson, you'll learn a new Japanese grammar using くします (ku shimasu) or にします (ni shimasu).

As you have already known, する (suru) or します (shimasu) means "to do (something)". It's normally connected with a noun to form a Group 3 verb.

For example, 勉強します (benkyou shimasu) means "to study", 洗濯します (sentaku shimasu) means "to do laundry".

It can also be combined with い-Adj, な-Adj or Noun to have another meaning which is what you are going to learn in this lesson.

Sentence Patterns

Let's see what are the sentence patterns...

い-Adj (~) く します
な-Adj に します
Noun に します

This grammar indicates that someone "turns" or "makes" something into a certain condition or state.

For い-Adjective, you first change it into its adverbial form by replacing the い (i) with く (ku), and then connect it to します (shimasu).

Whereas for な-Adj and Noun, append the particle に (ni) and then connect to します (shimasu).


Japanese Grammar ku shimasu / ni shimasu


音を 大きくします
oto wo ookiku shimasu

Meaning: I will increase the volume.


部屋を きれいにします
heya wo kirei ni shimasu

Meaning: I will clean the room.


砂糖の量を 半分にしました
satou no ryou wo hanbun ni shimashita

Meaning: I reduced the amount of sugar by half.


このボタンを押して、字を 二倍にします
kono botan wo oshite, ji wo nibai ni shimasu

Meaning: Press this button to double the word size.


zubon ga nagasugimasu kara, mijikaku shita hou ga ii desu yo

Meaning: The trousers is too long, therefore it's better to shorten it.


赤ちゃんが寝ていますので、テレビの音を 小さくしてください。
akachan ga nete imasu node, terebi no oto wo chiisaku shite kudasai

Meaning: Since the baby is sleeping, please lower the volume of the TV.


冷房をつけて、部屋を 涼しくしましょう
reibou wo tsukete, heya wo suzushiku shimashou

Meaning: Let's turn on the air-con and make the room cool.


テープを聞いて、発音を よくしたいと思います。
te-pu wo kiite, hatsuon wo yoku shitai to omoimasu

Meaning: I want to make my pronunciation perfect by listening to the tape.


値段はちょっと高いです。少し 安くしてください。
nedan wa chotto takai desu. sukoshi yasuku shite kudasai

Meaning: The price is a bit high. Please lower the price a little.

Differences between ~くします/~にします and ~くなります/~になります

い-Adj ~) く なります
な-Adj に なります
Noun に なります

Many people get confused about this Japanese grammar ~くします/~にします with another similar grammar ~くなります/~になります.

While ~くします/~にします indicates that someone "turns" or "makes" something into a certain condition or state, ~くなります/~になります indicates that something "becomes" a certain condition or state.

The main difference is that ~くします/~にします involves a person who make the action, whereas ~くなります/~になります just describes the change in condition or state.

Let's use some examples to explain the differences between these two Japanese grammars.


洗濯をしました。ズボン 短くなりました。
sentaku wo shimashita. zubon ga mijikaku narimashita

Meaning: I did the washing. The trousers becomes shorter.


長すぎましたから、ズボン 短くしました。
nagasugimashita kara, zubon wo mijikaku shimashita

Meaning: The trousers was too long, therefore I shortened it.

In example 1, I didn't physically do anything to shorten the trousers. It becomes shorter naturally after the washing. ~くなります is describing the state of the trousers.

In example 2, the state of the trousers is the same - becomes shorter. However, this change is made by me on purpose. I made the trousers shorter because it was too long.

Another difference to take note of is the particle used in the two Japanese grammars. For the first example, it just describes the state of something with くなります, therefore the particle が (ga) is used.

But when a person is involved for the change of state in the second example with くします, the particle を (wo) is used.

Another Example

Let say that you visit your friend's house and are having dinner with the family. Your friend's mother serves you a big bowl of rice.

You want to reduce the amount of rice as you know you cannot eat that much. How do you make the request?

The correct way to say it should be...

  • 食べられませんので、ご飯を 少なくしてください。 O
    taberaremasen node, gohan wo sukunaku shite kudasai O

    Meaning: As I cannot eat that much, please reduce the amount of rice.

If you were to use くなります, like the following...

  • 食べられませんので、ご飯を 少なくなってください。 X
    taberaremasen node, gohan wo sukunaku natte kudasai X

...this is totally wrong. You are thinking somehow like magic, the rice will become less by itself.

Selection/Decision: Noun に します

There is another meaning for the Japanese grammar Noun に します (Noun ni shimasu). It can also express a selection and/or decision.

Let's look at some examples...


kaigi wa suiyoubi ni shimasu

Meaning: I will set the meeting on Wednesday.


ryokou no mokutekichi wa hokkaidou ni shimashita

Meaning: I have decided Hokkaido to be our tour destination.


heya wa tsuin ni shimashou

Meaning: Let's select the twin room.


nomimono wa ko-hi- ni shimasu ka, ocha ni shimasu ka

Meaning: Would you like coffee or tea for drink?


A: ドレスはどんな色が好きですか。
doresu wa donna iro wo ga suki desu ka
Meaning: What kind of color do you like for the dress?

B: 黄色にします
kiiro ni shimasu
Meaning: I will select Yellow.

Related Page

Lesson 6: ようになる you ni naru.

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