Suru-Verbs (する-Verbs): How する Turns Nouns Into Verbs

Suru-verbs (する-verbs) are how Japanese turns nouns into verbs. Attach the light verb する to a verbal noun, and the result inflects as a single verb.¹ Learning the rule once unlocks a large slice of the lexicon, because thousands of Sino-Japanese compounds, actionable katakana loanwords, and a small set of native words all use the same template.²³

Overview

What a する-verb is

A verbal noun (動作性名詞 or 動詞的名詞, abbreviated VN) is "a noun to which the light verb suru (する, 'do') can be appended."¹ The combination produces a single verb. Its tense, aspect, and negation all live on する.²⁴

The noun itself is frozen. 勉強 ("study," the noun) plus する yields 勉強する ("to study," the verb), and only the する portion ever conjugates.⁴⁵

私わたしは毎日まいにち日本語にほんごを勉強べんきょうする。⁶
"I study Japanese every day."

NINJAL's term of art is 動詞的名詞 (verbal noun, VN), and the combination "VN + する" is called a VN phrasal verb.³

Why this is the most productive verb-formation pattern in Japanese

Verbal noun + する is the main way Sino-Japanese nouns and loanwords enter the Japanese verb system. Verbal nouns "need the light verb suru 'do' to formally realize tense, aspect, and modality."² Wikipedia, citing standard reference grammars, puts it bluntly: "new and borrowed verbs and adjectives are typically conjugated periphrastically as verbal noun + suru."¹

The class has thousands of members. The 漢語 (Sino-Japanese) stratum alone licenses several thousand サ変 candidates, and the 外来語 (loanword) stratum is open-class, so it grows every year.³⁷

する is a verb factory

Instead of memorizing each compound verb separately, learn する's paradigm once. Then you can conjugate every verbal noun in the dictionary. Every 勉強する, デートする, and 案内する uses the same handful of forms.²⁴⁵

What "サ変" means in a dictionary

When a paper dictionary tags an entry with サ変 or サ行変格活用 (sa-row irregular conjugation), it means this noun forms a verb by attaching する. The result conjugates like the irregular verb する.⁴⁸

That tag is the main reason a learner needs the label "サ変." The full conjugation paradigm of する itself belongs in the verb-classes article. Here, the tag simply signals that "this noun is a verbal noun."

The basic pattern: noun + する

The formula

The formula is VN + する, where VN is a verbal noun that names an action.⁴¹ Here is a small set of high-frequency verbs that follow this pattern. All are attested as verbal nouns with sa-row irregular conjugation:⁴⁵⁶

Verb	Reading	Meaning
勉強する	benkyō suru	to study
仕事する	shigoto suru	to work
結婚する	kekkon suru	to marry
旅行する	ryokō suru	to travel
練習する	renshū suru	to practice
電話する	denwa suru	to phone
質問する	shitsumon suru	to ask a question
連絡する	renraku suru	to contact

Each entry has a noun on the left and the inflectable する on the right. The boundary never changes, no matter what tense or politeness level the speaker uses.

How the verb conjugates

The noun is frozen; only する moves. The full inflectional paradigm is exactly the paradigm of する:⁴

Form	勉強する	デートする
Plain non-past	勉強する	デートする
Polite non-past	勉強します	デートします
Plain past	勉強した	デートした
Polite past	勉強しました	デートしました
Plain negative	勉強しない	デートしない
Te-form	勉強して	デートして
Conditional	勉強すれば	デートすれば
Potential	勉強できる	デートできる

The polite forms (勉強します, 勉強しました) follow the regular ます-form paradigm built on する's masu-stem し-. The te-form is して, because する is one of the three irregular verbs whose te-form does not follow the godan or ichidan rules. The potential is suppletive, meaning it uses a different root: する's potential form is できる, not the regular ×されられる.⁵ Every VN + する verb inherits this. 勉強できる, not ×勉強される, is "able to study."

Wikipedia's verb-conjugation reference groups VN + する verbs with the bare verb する as "Group A: Suru itself and compounds of it and free nouns."⁵ There is no separate paradigm to learn.

友達ともだちに電話でんわしました。⁶
"I called my friend."

毎日まいにちピアノを練習れんしゅうしています。⁶
"I practice the piano every day."

Which nouns can take する

Not every noun is a verbal noun. NINJAL's verbal-noun research identifies three reliable categories that produce サ変 verbs (する-based verbs):³

1. Sino-Japanese (漢語) two-kanji compounds that name an action: 勉強, 結婚, 旅行, 練習, 説明, 紹介, 案内, 計画, 注文, 確認.³⁵
2. Gairaigo (外来語) that name an action: デート, アップロード, コピー, キャンセル, チェック, クリック, インストール, シェア, メモ.⁹
3. Native 和語 in a small, lexicalized set: 噂する, 涙する, 旅する, 恋する.⁹

The defining property is syntactic: can the noun combine with する? It is not just about action meaning. NINJAL notes that even nouns that "don't represent actions" (意味, ランチ, お茶) can combine with する.³

The test is syntactic, not semantic

A clean learner filter is this: if a noun can answer "what activity is X?" or "what action does X name?", it is almost certainly a verbal noun. Concrete-object nouns like 本 (book), 車 (car), and りんご (apple) fail the test and do not take する.³

The three input strata

する works on three different vocabulary layers, which is the deeper reason it is so productive. The mechanism is the same. What changes is which words flow into it. These three layers map onto the four vocabulary strata of Japanese (wago, kango, gairaigo, konshugo). する is the verbalizer that all three productive strata route through.

Sino-Japanese (漢語) + する: the workhorse layer

This is the densest source. Two-kanji 漢語 compounds with action meanings form サ変 verbs essentially by default when the meaning supports it.²⁵ The list is long and includes many action verbs a learner meets in beginner and intermediate textbooks: 勉強する, 結婚する, 旅行する, 練習する, 説明する, 紹介する, 案内する, 計画する, 注文する, 確認する.³⁵⁶

Wikipedia's verb-conjugation reference describes Group A compounds as "usually, but not always, spelt with two more kanji if Sino-Japanese."⁵ The two-kanji shape and the on'yomi reading are strong, though not absolute, signals that a word may be サ変.

道みちを案内あんないします。⁶
"I will show you the way."

もう一度いちど説明せつめいしてください。⁶
"Please explain it once more."

Gairaigo (外来語) + する: the open-ended layer

This is where productivity is most visible, because new words enter the verb system every year. A katakana loanword that names an action takes する with no change to its form: デートする, アップロードする, ダウンロードする, コピーする, キャンセルする, チェックする, クリックする, インストールする, アップデートする, シェアする, メモする.⁹

The writing convention is consistent: katakana noun, hiragana する. Wikipedia summarizes the pattern as "new and borrowed verbs and adjectives are typically conjugated periphrastically as verbal noun + suru."¹

予約よやくをキャンセルしてください。⁶
"Please cancel my reservation."

週末しゅうまつに彼女かのじょとデートします。⁶
"I am going on a date with my girlfriend this weekend."

Native (和語) + する: the small, literary layer

The native stratum is short. The regular way Japanese coins a verb on a native root is direct 五段 or 一段 morphology (歩く, 走る), not a light-verb construction.⁹ The handful of 和語 + する verbs that do exist are mostly emotive or set expressions: 噂する (to gossip), 涙する (to shed tears), 旅する (to journey, poetic), 恋する (to be in love).⁹

Do not coin new 和語 + する verbs

The native list is closed. 噂する and 涙する are lexicalized survivors, not a productive template. A learner who needs a verb for a native concept should look for the existing 五段 or 一段 verb instead.⁹

Why three strata and not just one

する functions as a light verb that absorbs noun content from whichever stratum the language is importing from. The 漢語 inflow, which peaked in the Heian and Edo periods, and the 外来語 inflow, which is modern and ongoing, both used する as the entry route into the verb system.²¹ The native layer stays small because Japanese already has direct verb-derivation routes that 漢語 and 外来語 lack.

Shibatani (1990) frames this as a structural feature of the lexicon: a light verb is required because verbal nouns cannot carry tense, aspect, and modality directly.² Whatever stratum supplies the noun, する supplies the inflection.

The を-disappearance phenomenon

This is the question every beginner runs into and many textbooks skim past. 勉強する and 勉強をする are both correct. The difference is not meaning, but structure.

The two surface forms

Both 勉強する and 勉強をする are grammatical. Both are attested in standard corpora, and both translate as "to study."¹⁰⁶ Shimada and Kordoni (2003) call them the incorporated form (VN directly precedes する) and the unincorporated form (VN takes the accusative を).¹⁰

Form A: noun + する as one lexical unit

勉強する parses as a single verb. The verbal noun is incorporated into the predicate, so the combination behaves as one inflectable unit.¹⁰ This is the default form. It is by far the more frequent of the two in conversation and writing.¹⁶

Grimshaw and Mester (1988) describe the incorporated form as a light-verb construction in which する transfers its theta-roles, or participant roles, from the verbal noun.¹¹ In practical terms, Form A is the default choice when the noun does not need to be modified or counted.

Form B: noun + を + する as object + verb

勉強をする parses as "do study," with 勉強 as the direct object of する.¹⁰ The decisive consequence is that this form allows noun-internal modification: 難しい勉強をする ("to do difficult study"), 日本語の勉強をする ("to do Japanese study").¹⁰ Form A cannot accept those modifiers because its VN is not a free noun phrase (NP).

Shimada and Kordoni add a semantic filter: only activity-class and accomplishment-class verbal nouns allow the VN + を + する form. Achievement and state nouns do not.¹⁰

私わたしは毎日まいにち英語えいごの勉強べんきょうをする。⁶
"I study English every day."

難むずかしい勉強べんきょうをする。¹⁰
"I do difficult studying."

The diagnostic

Ask one question: does the verbal noun need a modifier or a counter? If yes, use noun + を + する. If no, use noun + する.¹⁰ The test follows from the syntax: Form A's incorporated VN cannot take adjectival or relative-clause modifiers, while Form B's VN can.¹⁰

Why you cannot stack two を

The Double-o Constraint (Harada 1973) bars two accusative-marked noun phrases in a single clause.¹²¹³ When 勉強する takes a real direct object such as 日本語, that object claims the only available を. The Form B variant then becomes unavailable.¹⁰¹²

In concrete terms, 日本語を勉強する is grammatical. ×日本語を勉強をする stacks two を on the same predicate and is ungrammatical.¹⁰

日本語にほんごを勉強べんきょうする。¹⁰
"I study Japanese."

Never stack two を on a suru-verb

×日本語を勉強をする is wrong. Once a real direct object is in play, Form A (noun + する) is the only legal option, because the Double-o Constraint blocks a second accusative を in the clause.¹⁰¹²¹³

Register and frequency note

勉強する dominates speech and writing in standard corpus observation.²⁷ 勉強をする is also standard, but it feels slightly more deliberate. Speakers use it when they want to foreground 勉強 as a thing being done rather than as a kind of doing. Once the modification test is settled, the remaining choice between Form A and Form B (with no modifier) is stylistic.¹⁰

The の-of variant: noun + の + noun + する

The Double-o Constraint creates one more surface variant a learner will see: a noun phrase modified with の, sitting as the object of する.

What the の form looks like

日本語の勉強をする ("to do Japanese study") puts a noun phrase modified with の as the direct object of する.⁶ Structurally, this is Form B (VN + を + する) with internal の-modification.¹⁰

Why it is not the same as Form A

The two readings attach in different places. 日本語を勉強する modifies the predicate: the object of studying is Japanese, a predicate-level argument.¹⁰ 日本語の勉強をする modifies the noun: the kind of study is Japanese-study, a noun-internal modification.¹⁰

The idiomatic English translation collapses both into "study Japanese," but Japanese keeps them apart. The の form is the only way to express the noun-internal reading without violating the Double-o Constraint.¹²

When to reach for の-of and when not to

Use noun + を + する with a の-modifier when foregrounding the kind of activity (日本語の勉強をする, 絵の勉強をする).⁶ Use noun + を + する without a modifier when foregrounding the activity itself.¹⁰ Use plain noun + する as the unmarked default. Choose Form B only when the modification test forces it.¹⁰

The ずる / じる sub-pattern

A small group of suru-verbs lenited, or softened, their consonant centuries ago and now look like ordinary ichidan verbs. English-language pages often skip this, which can confuse mid-N5 readers who meet 感ずる in a literary text.

What the pattern is

A small set of single-kanji 漢語 roots historically formed 〜する verbs. They voiced to 〜ずる via rendaku, then ichidanized to 〜じる.¹⁵ Wikipedia summarizes the change: "verbal nouns with a single-character root often experienced sound changes, such as -suru (〜する) → -zuru (〜ずる) → -jiru (〜じる)."¹

Attested members:¹⁴¹⁵⁵

Older サ変 form	Modern ichidan form	Meaning
感ずる	感じる	to feel
信ずる	信じる	to believe
禁ずる	禁じる	to forbid
命ずる	命じる	to order
論ずる	論じる	to discuss
応ずる	応じる	to respond

Wikipedia's verb-conjugation entry notes that these forms "behave more like upper (i-stemmed) ichidan verbs."⁵

How to read the dictionary entries

Modern dictionaries list both 感ずる and 感じる. 感じる is the modern default, and 感ずる is the formal or literary variant.¹⁴⁵ The ichidan form conjugates as a regular 一段 verb: 感じる, 感じない, 感じます, 感じて, 感じた.¹⁴ The older 感ずる still appears in formal writing and conjugates as the original サ変 pattern.⁵

In modern Japanese, the 〜じる variant is clearly dominant. One hobbyist source places the ratio at roughly three to one in favor of 〜じる, and Wikipedia's prose corroborates the direction even if the exact figure is not corpus-backed.¹⁵⁹

寒さむさを感かんじる。⁶
"I feel the cold."

私わたしはあなたを信しんじる。⁶
"I believe you."

Why this matters at N5/N4

感じる and 信じる are high-frequency verbs and pattern like ordinary ichidan verbs.¹⁴¹⁵ A learner does not need the etymology to inflect them correctly. Still, recognizing 感ずる and 信ずる as the older sibling forms prevents confusion when they appear in formal or literary text.⁵

Good to know

"I did it": する as a freestanding verb

する on its own means "to do" and takes a wide range of complements beyond the verbalizer use. テニスをする ("to play tennis"), ネクタイをする ("to wear a tie"), 音がする ("a sound is heard"), and 値段がする ("it costs") all use the bare verb.¹⁵ The VN + する pattern is a specialization of this general verb, not a separate construction.²¹

Why "×本する" is not a word

The noun that feeds する must be a verbal noun (動作性名詞 or 動詞的名詞). 本 (book) is a concrete object that does not pass NINJAL's syntactic test of free combinability with する, so ×本する is ungrammatical.³ A quick learner filter is this: if the noun cannot answer "what action does X name?" or "what activity does X label?", it does not take する.³

To express the intended meaning, use a real verb plus the noun as an object:

本ほんを読よむ。⁶
"I read a book."

Compound する-verbs inherit the irregular conjugation

Every VN + する verb conjugates exactly like する. 勉強する produces 勉強し (stem), 勉強して (te-form), 勉強しない (negative), 勉強した (past), and 勉強できる (potential, with the suppletive shift to できる).⁴⁵ Wikipedia's verb-conjugation entry places VN compounds in Group A alongside bare する. There is no separate paradigm to memorize.⁵

Polite-form shortcut: します attaches directly

The polite form is built on する's masu-stem (し-), not on the noun. 勉強します, デートします, and アップロードします all follow the same pattern.⁴ The noun never inflects, even in polite or past-polite forms. Only the する portion moves.⁴

Double を with a transitive suru-verb

The Double-o Constraint blocks two accusative-marked noun phrases in a single clause. So when a transitive VN + する verb takes a real direct object, the Form B variant disappears.¹⁰¹²¹³ The wrong form stacks both: ×日本語を勉強をする. The correct alternatives are 日本語を勉強する (Form A, the only legal choice when the real object is present) or 日本語の勉強をする (Form B, where 日本語 is moved inside the noun phrase with の):

日本語にほんごを勉強べんきょうする。¹⁰
"I study Japanese."

感じる and 信じる are sa-hen in disguise

Modern 感じる and 信じる look like ordinary ichidan verbs and inflect like ordinary ichidan verbs. But they descend from sa-hen ancestors (感ずる, 信ずる) via the suru → zuru → jiru sound change.¹⁴¹⁵¹ Formal and literary writing may still use the 〜ずる form, so a reader who recognizes the etymology can parse both shapes without confusion.⁵

Why textbooks rarely cover this fully

N5 textbooks introduce 勉強する, 結婚する, and 旅行する as vocabulary items rather than as instances of a rule.⁴¹⁶ The productivity claim, that any verbal noun + する is a verb, is typically named only when later lessons introduce 経験する, 利用する, and 提供する, which is mid-N4 territory.¹⁶ Calling out the rule at N5 closes that gap and turns dozens of "new" verbs into one pattern.

See also

• Japanese Verb Groups: 一段, 五段, and Irregular
• The Masu Form (ます): Polite Present and Future Tense
• The Te-Form in Japanese: Construction Rules
• Potential Form: ～られる, ～える, できる
• Onomatopoeia + する: Verbalizing Mimetic Words
• Wago, Kango, Gairaigo, Konshugo: The Four Vocabulary Strata of Japanese

References

Footnotes

1. Wikipedia, "Japanese grammar." https://en.wikipedia.org/wiki/Japanese_grammar ("a verbal noun is simply a noun to which the light verb suru can be appended"; periphrastic verbal-noun + suru pattern; suru→zuru→jiru sound-change note). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³

2. Shibatani, Masayoshi. The Languages of Japan. Cambridge University Press, 1990, pp. 215–217 (verbal nouns and the light verb suru). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹

3. 影山太郎 (Kageyama, Taro). 「日本語の動詞的名詞（サ変名詞）の文法的位置づけ：専用型と兼務型」. 国立国語研究所 (NINJAL), 2004. https://repository.ninjal.ac.jp/record/3109 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

4. Wiktionary entry for 勉強する. https://en.wiktionary.org/wiki/%E5%8B%89%E5%BC%B7%E3%81%99%E3%82%8B (sa-row irregular conjugation, transitive/intransitive suru-verb, Sinitic etymology). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

5. Wikipedia, "Japanese verb conjugation." https://en.wikipedia.org/wiki/Japanese_verb_conjugation (Group A "suru itself and compounds of it and free nouns"; Group C "ronzuru → ronjiru" behaving as upper-ichidan). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰

6. Jisho.org, sentence search with credited corpus tags (Jreibun, Tatoeba). https://jisho.org/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷

7. 国立国語研究所 (NINJAL). 「現代日本語書き言葉均衡コーパス」(BCCWJ). https://clrd.ninjal.ac.jp/bccwj/ ↩ ↩²

8. Weblio Japanese-language reference, entry for サ行変格活用 (citing Wikipedia article on Japanese verb conjugation). https://www.weblio.jp/content/%E3%82%B5%E5%A4%89%E5%8B%95%E8%A9%9E ↩

9. Japanese with Anime, "Suru Verbs." https://www.japanesewithanime.com/2021/12/suru-verbs.html ("the ~jiru suffix is far more commonly used than the ~zuru suffix in modern Japanese (around 3 times more)"). (limitation: hobbyist site) ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

10. Shimada, Atsuko, and Valia Kordoni. "Japanese 'Verbal Noun and Suru' Constructions." Proceedings of the Workshop on Multi-Word Expressions, ACL, 2003. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹

11. Grimshaw, Jane, and Armin Mester. "Light Verbs and θ-Marking." Linguistic Inquiry 19.2, MIT Press, 1988, pp. 205–232. ↩

12. Harada, Shin-Ichi. "Counter Equi NP Deletion." Annual Bulletin 7, Research Institute of Logopedics and Phoniatrics, University of Tokyo, 1973 (origin of the Double-o Constraint). ↩ ↩² ↩³ ↩⁴ ↩⁵

13. Poser, William J. "The Double-o Constraints in Japanese." Manuscript, University of Pennsylvania. http://www.billposer.org/Papers/oo.pdf ↩ ↩² ↩³

14. Wiktionary entry for 感じる. https://en.wiktionary.org/wiki/%E6%84%9F%E3%81%98%E3%82%8B ("Shift from 感ずる, a compound of 感 + する"; ichidan classification). ↩ ↩² ↩³ ↩⁴ ↩⁵

15. Wiktionary entry for 信じる. https://en.wiktionary.org/wiki/%E4%BF%A1%E3%81%98%E3%82%8B ("Shifted from 信ずる"; ichidan classification). ↩ ↩² ↩³

16. Tofugu, "Japanese Verb Conjugation Groups." https://www.tofugu.com/japanese-grammar/verb-conjugation-groups/ ("only two fall outside of the godan and ichidan verb groups: する and 来る"). (limitation: commercial blog) ↩ ↩²