Irregular Verbs する and 来る in Japanese

In Brief

Japanese has two essential irregular verbs: する (“to do”) and 来る（くる, “to come”). Their polite forms are します and 来ます（きます）. Learn them as complete form families rather than trying to apply a regular verb rule, and remember that する combines with many nouns: 勉強する (“to study”), 運動する (“to exercise”), and 料理する (“to cook”).

Overview

Most Japanese verbs follow one of two broad conjugation patterns, but する and 来る do not fit either pattern completely. “Conjugation” simply means changing a verb’s form to express ideas such as politeness, negation, or past time. These two verbs therefore need to be memorized separately. Fortunately, there are only two, and both are extremely common.

At A1 level, the most useful forms are します／しません／しました and 来ます／来ません／来ました. They let you talk about everyday activities, plans, and arrivals. Japanese often leaves out the subject when it is clear, so 毎日勉強します can naturally mean “I study every day” without a word for “I.”

The reach of する is much wider than English “do.” It turns many nouns—words that name things, activities, or ideas—into verbs. Meanwhile, 来る changes not only its ending but also the reading of its kanji: く in 来る, き in 来ます, and こ in 来ない. Recognizing those three readings is a major part of mastering the verb.

How It Works

The core polite forms

The polite ます style is a practical starting point for speaking with teachers, unfamiliar adults, colleagues, and service staff. Japanese does not have a separate future tense in these forms: the non-past form covers both habits and future events, with context supplying the time.

Function	する	来る
Dictionary/plain non-past	する	来る（くる）
Polite non-past	します	来ます（きます）
Polite negative	しません	来ません（きません）
Polite past	しました	来ました（きました）
Polite past negative	しませんでした	来ませんでした（きませんでした）

Thus 勉強します can mean “I study,” “I will study,” or “I’m going to study.” A time expression makes the intended meaning clearer: 毎日勉強します is habitual, while 明日勉強します refers to tomorrow.

The core plain forms

Plain forms are used in casual conversation and also inside longer sentences, even when the sentence as a whole is polite. The negative ending ない and past ending た are part of the verb rather than separate words.

Function	する	来る
Non-past affirmative	する	来る（くる）
Non-past negative	しない	来ない（こない）
Past affirmative	した	来た（きた）
Past negative	しなかった	来なかった（こなかった）
て-form	して	来て（きて）

The changing readings of 来 are easiest to remember in three families:

• くる: the dictionary form 来る
• き-: 来ます、来た、来て
• こ-: 来ない、来なかった

Do not treat 来る as an ordinary verb ending in る. Removing る and adding an ending will sometimes give the wrong form and, just as importantly, the wrong reading.

Using する by itself

By itself, する means “do,” “perform,” or sometimes “choose/decide on,” depending on the expression. The particle を marks the object—the thing directly affected by the action.

Pattern	Example	Meaning
何をする	何をしますか。	What will you do? / What do you do?
object + をする	宿題をします。	I do my homework.
choice + にする	コーヒーにします。	I’ll have coffee. / I’ll choose coffee.

In コーヒーにします, にする presents coffee as the choice or resulting decision. This is a common restaurant and shopping expression, although the broader uses of にする belong beyond the basic “do” meaning.

Noun + する compound verbs

A する compound consists of an activity or concept noun plus する. The noun supplies the main meaning, while する carries all the conjugation.

Noun	Noun meaning	Verb	Verb meaning
勉強	study	勉強する	to study
運動	exercise	運動する	to exercise
料理	cooking	料理する	to cook
掃除	cleaning	掃除する	to clean
洗濯	laundry	洗濯する	to do laundry
電話	telephone call	電話する	to call
旅行	travel	旅行する	to travel
予約	reservation	予約する	to reserve

In many common activity expressions, both noun + する and noun + を + する are possible:

• 日本語を勉強します。 — I study Japanese.
• 日本語の勉強をします。 — I do Japanese study/studying.
• 毎日勉強します。 — I study every day.

However, do not assume that every Japanese noun can freely take する. Learn established combinations as vocabulary. Also keep the particle required by the compound verb’s meaning: 友達に電話する (“call a friend”), ホテルを予約する (“reserve a hotel”), and 東京で勉強する (“study in Tokyo”).

Using 来る: destination and viewpoint

来る describes movement toward the speaker, toward the listener, or toward a place treated as the conversational center. The destination is commonly marked by に or へ:

• 友達が家に来ます。 — A friend is coming to my house.
• いつ日本へ来ましたか。 — When did you come to Japan?

The person or thing that comes is marked by が when stated. English speakers sometimes choose “come” according to English habits, but Japanese viewpoint matters. If the movement is away from the relevant center, 行く (“to go”) is normally the better verb.

Examples in Context

Japanese	English	Note
毎日勉強します。	I study every day.	Polite habitual する compound
今夜、宿題をします。	I’ll do my homework tonight.	Future meaning from context
朝、運動をしました。	I exercised in the morning.	Polite past
今日は料理をしません。	I’m not cooking today.	Polite negative
週末に部屋を掃除する。	I clean my room on weekends.	Casual/plain style
駅の近くのホテルを予約しました。	I reserved a hotel near the station.	予約する takes the reserved item with を
友達に電話して、話しました。	I called a friend and talked.	に marks the person called; して links actions
何をしていますか。	What are you doing?	している describes an ongoing action here
友達が来ます。	A friend is coming.	が marks who is coming
明日、姉が家に来ます。	My older sister is coming to my house tomorrow.	に marks the destination
日本に来ました。	I came to Japan.	Subject omitted because context supplies it
昨日は誰も来ませんでした。	Nobody came yesterday.	Polite past negative
パーティーに来る？	Are you coming to the party?	Casual question; rising intonation
ここに来てください。	Please come here.	来て + ください makes a polite request
来週また来ます。	I’ll come again next week.	Same 来ます, future time from 来週

Common Mistakes

Treating 来る like a regular る-verb

• Wrong: 来ます（くます）
• Right: 来ます（きます）
• Why: The kanji reading changes. Memorize 来る（くる）→ 来ます（きます） as a pair.

Building the negative form mechanically

• Wrong: 来ない（きない）
• Right: 来ない（こない）
• Why: The plain negative belongs to the こ- family. It is not made by simply attaching ない to き.

Conjugating the noun instead of する

• Wrong: 勉強ました。
• Right: 勉強しました。
• Why: In a noun + する compound, only する changes: 勉強する → 勉強します → 勉強しました.

Adding する to every activity noun

• Wrong: 音楽する。 (when you mean “listen to music”)
• Right: 音楽を聞く。
• Why: English can use broad verbs such as “do” or rely on context, but Japanese compounds are established lexical combinations. Learn 勉強する and 運動する as units; do not invent a する verb for every noun.

Using 来る when the viewpoint requires 行く

• Wrong: 明日、あなたの家に来ます。 when speaking from your own home and merely saying you will travel to the listener’s home
• Usually natural: 明日、あなたの家に行きます。 — I’ll go to your house tomorrow.
• Why: Japanese generally uses 行く for movement away from the speaker’s current or adopted viewpoint. The exact choice can depend on where the conversation is anchored, so learn whole situations rather than equating English “come” with 来る every time.

Mixing polite and casual endings without a reason

• Awkward: 昨日勉強したです。
• Right: 昨日勉強しました。 / 昨日勉強した。
• Why: Use the polite past しました, or the plain past した. Standard Japanese does not normally create a polite past verb by adding です directly to した.

Usage Notes

する versus やる

やる can also mean “do,” and it is common in casual speech: 宿題をやる (“do homework”) or スポーツをやる (“play/do sports”). する is the safer neutral choice for a beginner. やる can sound casual or rough in some settings and has other meanings, so it should not be substituted automatically.

Particles around する compounds

A compound can appear without を—勉強する—or as a noun phrase followed by をする—勉強をする. The version with を can give the activity more noun-like weight or allow a modifier: 試験の勉強をする (“do studying for the exam”). With many everyday compounds, both patterns are grammatical, but their frequency and nuance vary by word.

Script and readings

する is normally written in hiragana. 来る is commonly written with kanji, but くる also appears in informal writing and beginner materials. Furigana or a parenthetical reading is useful at first because the kanji’s pronunciation changes. Do not write forms such as 来ります; the correct polite form is 来ます.

Beyond the Basics: Forms You Will Meet Later

You do not need to produce all of these at A1, but seeing the system now prevents surprises later. The irregular stem continues into requests, ability, commands, and other constructions.

Function	する	来る	Typical meaning
て-form	して	来て（きて）	do and… / come and…; basis for requests
Volitional	しよう	来よう（こよう）	let’s do / let’s come
Conditional	すれば	来れば（くれば）	if [someone] does / comes
Imperative	しろ / せよ	来い（こい）	do it! / come!
Passive	される	来られる（こられる）	be done / be come to (context-dependent and less common)
Causative	させる	来させる（こさせる）	make/let do / make/let come
Ability	できる	来られる（こられる）	can do / can come

A particularly important point is that the usual ability form of する is できる, not すれる: 日本語で予約できます means “I can make a reservation in Japanese.” With a compound, 勉強できる means “can study.” 来られる can mean “can come,” and in casual speech you may hear 来れる（これる）. The shorter form is widespread conversationally, but 来られる is the standard form to learn first.

The construction 〜てくる combines the て-form of another verb with 来る. It can express movement toward the speaker (持ってくる, “bring”), an action done before returning (買ってくる, “go buy and come back”), or a change developing up to now (寒くなってきた, “it has started getting cold”). These meanings deserve separate study; they are not simply literal “come.”

Respectful language replaces these verbs in some formal settings. いらっしゃる can respectfully describe someone coming, while 参る（まいる） can humbly describe the speaker’s own coming or going. These are advanced register choices, not alternative A1 conjugations.

Practice Tips

1. Memorize three short chains aloud: する・しない・した・して, 来る・来ない・来た・来て, and します・しません・しました. Saying the forms as rhythms is more reliable than reconstructing them from a rule.
2. Build an activity diary. Write five true sentences with compounds such as 勉強する、運動する、料理する, then change each sentence from today to yesterday or tomorrow. This practices both conjugation and Japanese’s context-based time system.
3. Draw a movement scene. Put yourself, another person, and two locations on paper. Describe who 来ます and who 行きます. This makes viewpoint concrete and helps prevent direct translation from English “come” and “go.”

Related Concepts

This concept has no formal prerequisite or related concept listed in the current Japanese grammar map. Useful topics to study alongside it are:

• Godan verbs (u-verbs) — compare their regular consonant-changing pattern with these two irregular verbs.
• Ichidan verbs (ru-verbs) — learn why 来る may look like a regular る-verb but does not behave like one.
• Polite form ます — expand the polite forms used throughout this article.
• て-form — build requests and linked actions from して and 来て.
• た-form (past plain) — place した and 来た within the wider plain-past system.