する is one of the most frequently used verbs in Japanese, but its meaning changes completely depending on the particle that precedes it.
Look at these four sentences:
A. 変な音がする。 → There's a strange sound. B. テニスをする。 → I play tennis. C. コーヒーにする。 → I'll have coffee. D. 義務とする。 → Treat it as an obligation.
Same verb する, four different particles, four different meanings.
がする — Sensory Perception (Involuntary)
"A がする" expresses naturally occurring sensory perceptions — sounds, smells, tastes, physical sensations. You can't control them; they just happen.
| Example | Meaning |
|---|---|
| 変な音がする。 | There's a strange sound. |
| いい匂いがする。 | Something smells nice. |
| 寒気がする。 | I feel chills. |
| めまいがする。 | I feel dizzy. |
| 楽しみがする。 | I feel excited/anticipation. |
Key word: involuntary. The sound occurs on its own, the smell drifts over by itself, the dizziness just hits you — you don't decide.
Common collocations:
- 音がする (there's a sound)
- 声がする (there's a voice/feeling)
- 匂いがする (there's a smell)
- 味がする (there's a taste)
- 気がする (I have a feeling)
- 寒気がする (I feel chills)
- めまいがする (I feel dizzy)
をする — Active Action (Voluntary)
"A をする" expresses actively doing something — sports, work, appearance. You can decide whether to do it or not.
| Example | Meaning |
|---|---|
| テニスをする。 | I play tennis. |
| 仕事をする。 | I work. |
| 赤いネクタイをする。 | I wear a red tie. |
| 丸い形をする。 | It has a round shape. |
Key word: voluntary. You decide to play tennis, you choose to wear a tie.
がする vs をする: Instant Identification
| がする | をする | |
|---|---|---|
| Control | Involuntary (occurs naturally) | Voluntary (active action) |
| Type | Sounds/smells/sensations | Sports/work/appearance |
| Example | 音がする | テニスをする |
にする — Decision / Choice
"A にする" expresses making a decision or choice — picking one option from several.
| Example | Meaning |
|---|---|
| コーヒーにする。 | I'll go with coffee. |
| 旅行先はパリにする。 | I'll choose Paris as the travel destination. |
| たばこをやめることにした。 | I decided to quit smoking. |
The core of にする is choosing/deciding. Picking coffee from a menu, deciding to quit smoking in life — both use にする.
ことにする vs ことになる
| ことにする | ことになる | |
|---|---|---|
| Subject | You decide yourself | Decided for you / happens naturally |
| Example | たばこをやめることにした | 来月転勤することになった |
| Translation | I decided to quit smoking | I'm being transferred next month (company decided) |
とする — Assumption / Treating As
"A を B とする" or "A と B (を) する" means assuming A is B or treating A as B.
| Example | Meaning |
|---|---|
| このことを義務としてください。 | Please treat this as an obligation. |
| 毎月5日を締め切りとする。 | The deadline shall be the 5th of each month. |
| 仮にAとする。 | Let's assume it's A. |
とする is very common in formal contexts — contracts, regulations, and academic writing.
ようとする — About to / Trying to
とする also has an important derived use: ようとする = about to do something / trying to do something.
- 卒業しようとする学生 → Students who are about to graduate
- ドアを開けようとしたら、鍵がかかっていた。 → I was about to open the door, but it was locked.
Overview of All Four Patterns
| Particle + する | Core Meaning | Key Word |
|---|---|---|
| がする | Sensory perception | Involuntary |
| をする | Active action | Voluntary |
| にする | Decision/choice | Choose/decide |
| とする | Assumption/treating as | Assume/stipulate |
Self-Test
Q1. "いい匂い＿する。" What particle goes in the blank?
Show answer
が. A smell drifts to you naturally — you can't control it — so it uses がする.
Q2. At a restaurant, you say "私はカレー＿する。" What particle fills the blank?
Show answer
に. Choosing curry from the menu is making a decision/choice, so you use にする.
Q3. What does "たばこをやめることにした" mean? Why not ことになった?
Show answer
It means "I decided to quit smoking." ことにした is used because this is a decision you made yourself. If you said ことになった, it would imply the decision was made for you (as if someone else or circumstances forced you to quit) rather than being your own resolution.
Summary
- がする = involuntary sensory perceptions (sounds, smells, sensations)
- をする = voluntary active actions (sports, work, appearance)
- にする = choice/decision (picking from options)
- とする = assumption/treating as (common in formal contexts)
- Same verb する, different particle = different meaning — the key is agency and context