The を Particle: Direct Object
The を particle is the Japanese direct object marker. It is the case particle (格助詞, kakujoshi) that flags the noun a transitive verb acts on.1 It also marks two related spatial roles with specific verb classes: the path of motion (公園を歩く "walk through the park") and the source of motion (家を出る "leave the house").1 2
Overview
Learners often meet を first as "the object particle" and then run into sentences like 公園を歩く, where 歩く is intransitive and there is no object to mark. The three uses look contradictory until you notice their shared job: を flags the noun the verb operates on, whether that noun is a patient, a region travelled through, or a place left behind.1 3 Reading the particle this way turns the path and source uses from exceptions into the same rule applied to different verb classes.
What を actually marks
を is a 格助詞 (kakujoshi, "case particle"). In traditional school grammar (学校文法, gakkō bunpō), the 格助詞 mark grammatical roles on noun phrases: が, を, に, で, へ, と, から, より, まで.4
In its canonical use, を marks the accusative case: the direct object (直接目的語, chokusetsu mokutekigo) of a transitive verb (他動詞, tadōshi), the noun on which the verb's action is performed.1 2
本を読む。5
"I read a book."
The same particle also marks the path of motion with intransitive motion verbs and the source of motion with verbs of egress.1 2 6 All three uses share one frame: を marks "the noun the verb operates on," whatever that operation looks like for the verb class involved.1 3
Tofugu, Bunpro, and most beginner pages treat path-を and source-を as quirky extensions of "the object particle." The Japanese Dictionary of Basic Japanese Grammar treats them as one case marker with three argument types.1 The second framing scales better: once you can read を as "this is the noun the verb is about," the path and source uses stop feeling like exceptions.
Historically, the modern direct-object use of を is widely held to come from an earlier "through, along" meaning. The path-of-motion use directly continues that older function. The canonical direct-object use is the extension that grew out of it.2
Pronunciation: written wo, pronounced o
In modern standard Japanese, the kana を represents the syllable /o/ and is pronounced identically to お.7 8 The romanisation "wo" reflects only the historical reading and the kana row the character sits in (the わ-行, wa-gyō). Modern Tokyo speech does not realise [w] in this kana.7
A faint [wo] allophone, or pronunciation variant, appears in two narrow registers: emphatic enunciation (singers exaggerating the syllable for prosodic weight) and some dialectal varieties.7 9 In standard Tokyo speech and in NHK broadcast pronunciation, the realisation is plain [o].7
Modified Hepburn romanises the particle as o, not wo, because it romanises what is said rather than what is written.7 The "wo" form survives in IME romaji input: typing wo produces を, while typing o produces お. That is why beginner-facing materials often keep "wo" as the input mnemonic.9
お茶を飲む。10
"I drink tea."
In modern Japanese the kana を has no other use: it appears only as this particle, never inside word stems or loanwords.11 8 4
Register, JLPT level, and scope
を is register-neutral. It appears unchanged from intimate spoken Japanese through legal prose. Casual speech differs only in whether the particle is spoken or dropped (see Good to know).1 12
The particle is present from N5 onward in every standard textbook sequence. Genki I introduces it in chapter 3 and the path-of-motion use in chapter 10; Minna no Nihongo I introduces it in lesson 6 and the motion-verb use in lesson 13.5 13 It appears in the official JLPT N5 practice workbook in the first reading-comprehension passages without a separate gloss. The test does this only for grammar at or below the candidate level.14
を does not stack with は or も on the same noun. When a direct object is topicalised with は or marked as "also" with も, the case particle を drops. The focus particle takes the slot. *はを and *もを are ungrammatical in modern standard Japanese.1
The same overwrite rule applies to が. It distinguishes the two least-oblique case particles (が, を) from the oblique case particles (に, で, へ, から, まで). The oblique particles all stack with は: にも, には, では, へは, からは are all grammatical.1
パンを食べた。5
"I ate bread."
パンは食べた。1
"As for the bread, I ate it."
パンも食べた。1
"I also ate bread."
How を works: the direct-object job
The basic frame: [X を] [transitive verb]
The canonical use of を is [noun phrase を] [transitive verb]. Here, the noun phrase is the patient of the action.1 5 13
The subject (the agent) is marked separately by が or topicalised by は. を sits on the object regardless of how the subject is expressed.1 This is why the subject is so often dropped in Japanese conversation while the object often stays visible with を: the particle uniquely identifies the patient role.3
私はパンを食べた。5
"I ate bread."
手紙を書きます。13
"I write a letter."
何を食べますか。10
"What will you eat?"
漢字を覚える。10
"I memorize kanji."
Word order is flexible because を marks the role
Japanese word order is flexible because case particles, not position in the sentence, identify grammatical roles. The pair 私はパンを食べた and パンを私は食べた both mean "I ate bread"; what changes is emphasis, not who ate what.1 2
This is the payoff of learning を early. Once you know that を locks the object role onto its noun, scrambled or topic-fronted sentences stop being puzzles.3 The verb still has to stay at the end of the clause. The noun phrases before it are what move around.2
私はパンを食べた。1
"I ate bread."
パンを私は食べた。1
"I ate bread."
The second sentence puts パンを first for emphasis. The basic meaning is identical because を, not position, names the object.
を with transitive verbs only (canonical case)
In the canonical case (setting aside the path-of-motion and source-of-motion extensions below), only 他動詞 (tadōshi, transitive verbs) take a を-marked argument.1 15
A standard N5 set of transitive verbs makes the rule concrete: 食べる (eat), 飲む (drink), 読む (read), 書く (write), 見る (watch / look at), 聞く (listen to), 買う (buy), 売る (sell), 作る (make), 勉強する (study).5 13
Structurally, a transitive verb describes an event with two arguments. The second argument (the patient) is affected by the action, and that second argument is marked by を.2 An intransitive verb (自動詞, jidōshi) has only one argument, which is marked by が. In the canonical case, the rule works both ways: a transitive verb selects を, while an intransitive verb selects が, never を.2 15
水を飲む。5
"I drink water."
映画を見る。10
"I watch a movie."
車を買った。5
"I bought a car."
The exceptions to "no を with intransitive verbs" follow a clear pattern. They are the path-of-motion and source-of-motion uses below, both restricted to specific verb subclasses.1 2 16
The path-of-motion を: 公園を歩く
The pattern: [place を] [motion verb]
With a closed class of motion verbs (verbs of motion through space), を marks the area or route traversed by the motion.1 2 3 17 The technical term for this role is perlative, meaning motion through or along something. The rest of this article uses "path of motion" or "path through space."
Core inventory: 歩く (walk), 走る (run), 泳ぐ (swim), 飛ぶ (fly), 渡る (cross), 通る (pass through), 散歩する (stroll), 登る (climb), 下る (descend), 曲がる (turn).6 3 9 17
The learning-friendly reframing is simple: the motion verb is "done to" the location. So the place becomes the direct object of the motion verb in Japanese syntactic logic, even though English would use a preposition such as through, across, or along.3 This is the same case-marker logic as canonical を, applied to a different argument type.1 2
公園を歩く。9
"I walk through the park."
川を泳ぐ。17
"I swim across the river."
橋を渡る。18
"I cross the bridge."
空を飛ぶ。4
"Something flies through the sky."
階段を上る。9
"I go up the stairs."
The shared idea is that を with a motion verb indicates a point of passage, not an actual destination.17 The verb's action sweeps across the whole region, or the relevant part of it, named by the を-marked noun.2 17
Why an "intransitive" verb can still take を
歩く, 走る, 泳ぐ, 飛ぶ are classified as 自動詞 (jidōshi, intransitive verbs) because they describe a motion that does not affect a patient.2 16 So path-of-motion を can look like a violation of "intransitive verbs take が, not を."15
The resolution is that the path is not a patient. It is the region the motion is "carried out through."2 16 17 Linguistic analyses describe this as a separate path slot in the verb's structure. Historically, it preserves the older "through, along" function that the modern object use grew out of.2 16 For the learner, the practical fact is simple: the verb is still intransitive (the path does not change because someone walks across it), but it accepts an extra [place を] slot.2 16
An intransitive motion verb only accepts を on a noun that can be understood as a path or region of motion. Time expressions cannot fill that slot: ×昨日を走った ("ran yesterday-ACC") is ungrammatical because a time expression is not a path.16
鳥が空を飛んだ。4
"The bird flew through the sky."
毎日公園を走った。17
"I ran through the park every day."
In the first example, が marks the subject and を marks the path. The verb stays intransitive. Two case particles mark two different argument roles in one clause.
Path-を vs destination-に vs direction-へ
Three particles mark three spatial relations with motion verbs. The distinction maps onto a clear three-way meaning split.1 18
- Path-を marks the region or route traversed (公園を歩く "walk through the park").
- Destination-に marks the arrival point of a motion verb (公園に行く "go to the park"; with 歩く, 公園に歩く is marginal because 歩く does not include an endpoint in its meaning).
- Direction-へ marks the direction faced or moved toward, without entailing arrival (公園へ歩く "walk toward the park").
A useful learning gloss: with を, the feet move within the marked location. With に or へ, the feet move toward it from outside.18 The contrast is which spatial role the noun plays in the motion event, not which particle is "correct."1 18 A full に / で / へ comparison belongs to the dedicated articles for those particles. This section establishes only that path-を is one corner of the spatial-particle system and does not contradict the destination or direction uses.18
公園を歩く。9
"I walk through the park."
公園へ歩く。18
"I walk toward the park."
公園に行く。18
"I go to the park."
The source-of-motion を: 家を出る
The pattern: [origin を] [egress verb]
With verbs of egress, departure, or graduation (another closed class), を marks the place, institution, or vehicle that someone leaves behind.1 6 17
Core inventory: 出る (exit, leave), 降りる (get off, descend), 卒業する (graduate from), 離れる (leave, depart from), 立つ (depart from, in fixed uses such as 旅に立つ).1 6 17
The meaning is this: the noun marked by を is the location the verb's action is "about," specifically the point of separation. As with path-of-motion, the marked noun is not a patient. The house is not "exited at," and nothing changes about the house. But it is the spatial argument the verb operates on.1 2
家を出る。6
"I leave the house."
電車を降りる。6
"I get off the train."
大学を卒業した。17
"I graduated from university."
国を離れる。1
"I leave the country."
Why this is not a contradiction
As with path-of-motion を, source-of-motion を does not contradict the "no を with intransitive verbs" rule because the marked noun is not a patient.1 2
出る is intransitive: the door is not "exited at," and nothing about the location changes by being left.1 16 The transitive counterpart of 出る is 出す (take out, send out). It takes a true direct object: 手紙を出す ("send a letter") is canonical accusative-を, not source-of-motion.1 15
部屋を出た。6
"I left the room."
手紙を出した。1
"I sent a letter."
Two sentences, same kana, two different roles for を: the intransitive 出る takes source-of-motion を on its origin. The transitive 出す takes object-marking を on its patient. This is the wider 自動詞・他動詞 pair system at work: each member of a pair selects its own particle.2 16 15
Source-を vs から: a subtle nuance
For verbs that allow both, 家を出る and 家から出る both translate as "leave the house," but the nuance is different. This is the distinction taught across the major textbook tradition rather than a sharp result from the academic literature.1 6 9
Source-を foregrounds separation from the origin as a completed act: the speaker is leaving and is now away from it. This is why graduation (大学を卒業する) and decisive departures (国を離れる) prefer を over から.1 6
から foregrounds the starting point as one end of a path: "starting from the house." It is more neutral about whether the departure is complete. It is also the natural particle when a destination is specified.6 9
For 卒業 specifically, 大学を卒業する is the strongly preferred phrasing. 大学から卒業する is marked and rare.1 6 The egress-verb class already carries the meaning of separation, so the origin noun naturally takes を.2 16
家を出る。6
"I leave the house."
家から学校に行く。9
"I go from home to school."
In the second example, から marks the starting point of a longer path and pairs naturally with destination-に. A full から treatment is its own article. This section establishes only the contrast at the source-of-motion edge.
The no-を rule with intransitive verbs
Most intransitive verbs cannot take を at all
Outside the path-of-motion and source-of-motion subclasses above, intransitive verbs (自動詞, jidōshi) cannot take a を-marked argument.2 16 15 The thing that changes state is marked by が, not を.15
Canonical contrasts:15
- ×ドアを開く / 〇ドアが開く ("the door opens": 開く is intransitive; the door is the thing that opens, marked with が).
- ×電車を止まる / 〇電車が止まる ("the train stops": 止まる is intransitive).
- ×電気をつく / 〇電気がつく ("the lights come on": つく is intransitive).
ドアが開く。15
"The door opens."
電車が止まった。15
"The train stopped."
The rule is structural in Japanese: a verb stem is fixed as either transitive or intransitive, and the particle reflects that. There is no "the door opens itself / I open the door" alternation on a single verb. Japanese uses two different verbs for the two meanings.2 16 15
The 自動詞・他動詞 pair table you actually need
A core set of high-frequency N5 verbs comes in 自動詞・他動詞 (jidōshi / tadōshi, intransitive / transitive) pairs that share a stem.2 16 15 The transitive member takes を on its patient. The intransitive member takes が on the noun that undergoes the change. Learning the pair, not a single verb, is what unblocks the particle choice.15
These ten are the practical working set for N5:
| Intransitive (自動詞, takes が) | Transitive (他動詞, takes を) | Gloss |
|---|---|---|
| 開く (aku) | 開ける (akeru) | open |
| 閉まる (shimaru) | 閉める (shimeru) | close |
| 始まる (hajimaru) | 始める (hajimeru) | begin |
| 終わる (owaru) | 終える (oeru) | end |
| 落ちる (ochiru) | 落とす (otosu) | fall / drop |
| 入る (hairu) | 入れる (ireru) | enter / put in |
| 出る (deru) | 出す (dasu) | exit / take out |
| 止まる (tomaru) | 止める (tomeru) | stop |
| 付く (tsuku) | 付ける (tsukeru) | become attached / attach |
| 消える (kieru) | 消す (kesu) | disappear / turn off |
The full inventory of pair-formation morphology (the -aru / -eru pattern, the -ru / -su pattern, and others) belongs to a dedicated transitivity-pairs treatment.16 15 For を, the practical rule is the table above: pick the verb that matches the argument you want to talk about. The particle follows.
授業が始まった。15
"Class started."
先生が授業を始めた。15
"The teacher started class."
電気がついた。15
"The lights came on."
私は電気をつけた。15
"I turned on the lights."
Why English speakers default to the wrong one
English uses the same verb form for both members of a transitivity pair: "the door opens" and "I open the door" both use "open."15 Learners trained by English reach for を with the intransitive Japanese member out of habit, producing the canonical N5 error.15
In Japanese, the pair is two verbs with different argument structures, and the particle is fixed by the verb. There is no "I-open" version of 開く. The transitive sense uses 開ける.2 16 15
×ドアを開く is ungrammatical. 開く is intransitive and cannot take を. The fix is to pick the verb that matches the sentence: 開ける ("I open the door") with を, or 開く ("the door opens") with が.15
The learning takeaway: do not pick the particle first. Pick the verb first. Choosing 開く commits the sentence to が. Choosing 開ける commits the sentence to を. The pair is the unit of memorisation.
ドアを開ける。15
"I open the door."
ドアが開く。15
"The door opens."
Good to know
Why the kana を survived the 1946 spelling reform
The 1946 cabinet directive 『現代かなづかい』 (reissued and amended as 『現代仮名遣い』 in 1986) consolidated most pre-reform wo-row kana into the お-row in modern spelling. But it preserved を for the object particle alone.11 8 This is why を almost never appears inside a word stem in modern Japanese: it is reserved as a grammatical marker.8 4
The pre-reform spelling system 『歴史的仮名遣い』 (historical kana usage) used を inside word stems to spell historical /wo/ syllables that had merged with /o/ in pronunciation. The 1946 reform standardised those spellings to お. The few surviving stem-internal を appearances in modern Japanese are essentially fossils in personal names.8
The preservation of を for the particle is an intentional orthographic exception. Even though the kana represents the same /o/ sound as お, keeping it as a dedicated particle kana makes Japanese text easier to parse visually. を flags "object particle here" without the reader having to distinguish it from a homophonous noun-internal /o/.11 8
Typing を on a Japanese IME
To produce the kana を on a romaji-input Japanese IME (Google Japanese Input, Microsoft IME, macOS Japanese), type wo, not o.9 Typing o produces お.9 This is the one place the "wo" romanisation matters in modern Japanese: it is the IME input form, not the pronunciation.9
を drops in casual speech
In casual spoken Japanese, the object particle を is frequently dropped, especially in questions and short back-and-forth utterances.12 3 ご飯食べた? ("did you eat?") in place of ご飯を食べた? is the textbook example.12
Only a closed set of particles can be dropped this way: が, を, に, へ.12 The omission is governed by recoverability: the listener has to reconstruct the dropped role from context.12
This drop is conversational only. を stays in writing, formal speech, or any text where the role of the noun cannot be inferred from context.12 A full treatment of particle drop in colloquial Japanese is its own topic.
ご飯食べた?12
"Did you eat?"
を is never replaced by は or も; it is overwritten
When a direct object is topicalised with は or marked as "also" with も, the case particle を drops. The focus particle takes its slot without stacking.1 *はを, *もを, *をは, *をも do not exist in modern standard Japanese.1
This is the same overwrite rule that applies to が. The two least-oblique case particles (が, を) disappear under topic or focus marking. The oblique case particles (に, で, へ, から, まで) stack with は: にも, には, では, へは, からは, までは are all grammatical.1
パンを食べた。5
"I ate bread."
The topicalised form is パンは食べた; the "also"-marked form is パンも食べた. In both cases, を is gone, not hidden behind the focus particle.
Using を with a stative predicate
The most common N5 error driven by English habits is marking the object of a stative predicate (好き, 嫌い, 上手, 下手, 欲しい, わかる, できる, ある, いる) with を because the predicate looks transitive in English. The correct particle is が. The wrong form is ×日本語を好きです; the right form is below.15
日本語が好きです。15
"I like Japanese."
The が side of the contrast belongs to the が-particle article. The を side is simply that を is not licensed with stative predicates.
Using を with an intransitive verb
The second canonical N5 error is marking the argument of an intransitive verb (outside the path and source uses above) with を. The wrong form is ×ドアを開く. The fix depends on the intended meaning: 開ける with を if the speaker is opening the door, or 開く with が if the door opens on its own.15
ドアを開ける。15
"I open the door."
Pronouncing を as "wo" in normal speech
Pronouncing 本を読む as hon wo yomu with an audible [w] marks the speaker as a learner whose romanisation has shaped their pronunciation.7 The standard Tokyo realisation is plain [o]: hon o yomu.7 The [wo] allophone belongs to emphatic enunciation (sung lyrics, exaggerated speech) and some dialects, not to ordinary conversation.7 3
"Type wo, pronounce o"
The mnemonic keeps the keyboard fact (you type wo to get the particle kana) separate from the speech fact (you say [o], not [wo]).7 9 Holding the two together as one rule stops the kana-to-mouth feedback loop that produces the [wo] mispronunciation.
See also
- The で Particle: Means and Location of Action
- The も Particle: Also, Too
- は vs が in Japanese: A Beginner's First Pass
- Topic vs. Subject in Japanese: The Hidden Slot
- How Japanese Grammar Works: A Big-Picture Overview