くする

くする means make something become. It is a JLPT N4 Japanese grammar pattern used to make an i-adjective quality happen to something.

This grammar point often appears in conversation, written explanations, formal notices, and JLPT-style reading questions. If you want to make an i-adjective quality happen to something, くする is a useful pattern to learn after the N5 basics.

What does くする mean?

Use くする when you want to make an i-adjective quality happen to something.

Natural translations include:

• to make something
• to make something
• to make something

The exact English translation changes with context. Focus on what the grammar point does in the sentence first, then choose the English phrase that sounds natural.

How to form くする

i-adjective stem + くする

Examples of the pattern:

• 安くする
• 大きくする
• 早くする

Pay attention to the word form before the pattern. Many JLPT N4 mistakes happen because the meaning is understood, but the grammar is attached to the wrong form.

When is くする used?

Use くする in situations like:

• explaining a condition, reason, decision, or time relationship
• making a sentence more specific than a basic N5 pattern
• understanding natural Japanese in conversation or reading

Tone and register:

• neutral unless the grammar itself is marked as casual, humble, honorific, or formal
• Common in daily speech, textbook examples, and JLPT N4 reading questions

くする example sentences

• 音を小さくしてください。 — Please make the sound quieter.
• 部屋を明るくしました。 — I made the room bright.
• 値段を安くしてください。 — Please make the price cheaper.
• 字を大きく書いてください。 — Please write the characters bigger.
• 出発時間を早くしました。 — I made the departure time earlier.

Read the Japanese sentence first, then check the English translation. Try to notice what the grammar point contributes: condition, timing, limitation, possibility, decision, politeness, or emphasis.

Nuance of くする

The key nuance is means make something become a certain i-adjective state.

This matters because くする may look simple in English, but the Japanese form tells you whether the speaker is describing a time, a condition, a decision, a possibility, or a social relationship.

For example:

• In context, くする helps make the sentence more precise than a direct English translation.
• Compared with になる, it has a different focus even when both patterns appear in similar sentences.

くする vs になる

Both くする and になる can appear in related sentences, but they are different.

くする:

• is the target JLPT N4 pattern in this lesson
• carries the specific nuance explained above

になる:

• is useful for comparison because learners often mix it up
• may use a different form, tone, or sentence focus

Quick contrast examples:

• Target pattern: 音を小さくしてください。 — Please make the sound quieter.
• Related pattern with になる: compare the form and ask whether the sentence is about timing, condition, ability, decision, or politeness.

If you are unsure which one to use, identify the main job of the sentence before translating it into English.

Common mistakes with くする

Watch out for these mistakes:

• Using it with the wrong verb, noun, or adjective form
• Confusing it with になる because the English translation can look similar
• Translating it too literally instead of reading the whole sentence context

A good study habit is to write one short sentence and then change only the grammar point. This makes the difference between similar patterns easier to feel.

Is くする on the JLPT?

Yes. くする is commonly taught as JLPT N4 grammar.

That means learners should be able to:

• recognize it in reading
• understand its nuance in context
• use it in simple original sentences

For test preparation, do not only memorize the English gloss. Practice identifying the words around the grammar point, because JLPT questions often test structure and context together.

Practice questions for くする

Try making your own sentences with these prompts:

• Write one sentence using the basic pattern.
• Change the sentence into polite or casual style if possible.
• Compare it with the related pattern from the comparison section.

Keep the sentences short at first. Once the form feels natural, add time words, places, reasons, or contrast to make the sentence more realistic.

Learning path for くする

Use くする as part of your JLPT N4 change, decision, and intention grammar toolkit. Track who controls the change or decision in くする. Some patterns show natural change, some show personal effort, and others show a decision made by someone or by circumstances.

A good review order is: first make one short sentence with くする, then compare it with ことになる, and finally add にする or ようと思う to see how the nuance changes.

For practice, write one sentence that uses くする in its most literal meaning, one sentence that changes the subject or time expression, and one sentence that contrasts it with one of the related patterns below.

Related grammar to review next

• ことになる — connects to change, decision, planning, or effort over time.
• にする — connects to change, decision, planning, or effort over time.
• ようと思う — connects to change, decision, planning, or effort over time.
• 意向形 — connects to change, decision, planning, or effort over time.

Learn くする with Hane

If you want to review くする together with the related patterns above, Hane helps you practice Japanese in short, focused sessions.

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