Focus Particles: こそ, さえ, すら, だに
The focus particles こそ, さえ, すら, and だに belong to the same family of とりたて詞 (focus or highlighting particles). But only three of them mean "even"; the fourth means something else entirely.1 To sort them out, track two axes: what kind of focus each one marks, and how formal it sounds.
Overview
とりたて詞 (also called とりたて助詞, focus particles) are particles that highlight one element and color it with the speaker's attitude toward it. NINJAL describes とりたて表現 as expressions that convey meanings such as 「それに限られる。他は違う」(it is limited to that; others are different) or 「極端なものである」(it is an extreme case).1 The category includes だけ, しか, でも, なんか, まで, さえ, なんて, ぐらい, も, and は.1
In school grammar (学校文法) these same words are mostly taught as 副助詞 (adverbial particles); とりたて詞 is the descriptive-linguistics name for the group.2 The label matters less than the shared behavior: these particles express the speaker's stance toward an element, not its grammatical case relationship.2
The とりたて詞 family at a glance
This article focuses on four members, and they do not all do the same job.
- こそ: emphasis and positive identification ("this very one").3
- さえ: scalar "even", the everyday form.4
- すら: scalar "even", formal and written.5
- だに: scalar "even", archaic and frozen.6
The big split runs between こそ and the rest. さえ, すら, and だに are scalar "even" particles: they cite an extreme or surprising case and let you infer the rest. こそ instead singles out which element is the right one. It does not sit on that scale at all.63
Two axes to keep straight
The first axis is the kind of focus a particle marks. 大辞泉 defines だに's scalar sense as 「軽い事柄をあげて他のより重い事柄のあることを類推させる意を表す」(cite a light or minor case to make one infer the existence of heavier ones).6 That 類推 (inference from an extreme example) is exactly what binds さえ, すら, and だに together. By contrast, こそ 「ある事柄を取り立てて強める意を表す」(singles out and emphasizes a particular matter). It marks identification, not a scale.3
The second axis is register. The same scalar "even" sense climbs a ladder: casual さえ, formal written すら, and frozen-literary だに. すら is more literary than さえ;7 だに is classical and survives only in set phrases.89 This ladder is the organizing frame for everything below.
First ask whether you mean "even" (a scalar extreme) or "exactly this one" (identification). If you mean "even", ask how formal the context is. The first question sorts out こそ; the second orders さえ, すら, and だに.
こそ: positive identification, not "even"
こそ is the odd one out. Pin it down first, because learners often file it next to さえ as another "even" word. It is not.
Why こそ sits apart from さえ/すら/だに
大辞泉 (係助詞 こそ) gives its core sense as 「ある事柄を取り立てて強める意を表す」(expresses the meaning of singling out and emphasizing a certain matter).3 This is identification and emphasis of which one. It is not the placement of an extreme case on a scale.
今こそ実行にうつすべきだ。3
"Now is precisely the time we should act."
君こそが真の勇者だ。3
"You are the true hero, you of all people."
Where さえ, すら, and だに say "even X, so naturally the rest follows", こそ says "X is precisely the one." There is no 類推, no scalar inference. One further practical marker: こそ works with affirmative meaning and is not used to emphasize a negative.3 That already separates it from the すら〜ない and だに〜ない patterns below. The full forms (君こそ, こちらこそ, からこそ, and the contrastive 〜こそ〜が) belong to the dedicated こそ deep dive.
さえ: the everyday "even" (the reference point)
さえ is the baseline for the other two scalar particles, so it gets a single paragraph here rather than a full treatment.
What さえ does, in one paragraph
さえ is the everyday scalar "even": it cites a case, usually an extreme or surprising one, and implies the rest by inference.4 It also carries the さえ〜ば conditional ("if only / as long as", marking a sufficient condition). This is the one job すら and だに do not share.4
このロボットは走ることさえできます。4
"This robot can even run."
チケットさえあれば入れます。4
"As long as you have a ticket, you can get in."
The second sentence is the conditional use. Keep it in mind, because this is where すら parts ways with さえ. The でさえ form (さえ after a noun) and the full conditional treatment live in the さえ deep dive. For the comparison, all you need is that さえ is the neutral, spoken-and-written default.7
すら: the formal/written "even"
すら is the member of this family learners most often look up, usually in contrast with さえ. It does さえ's job, but in a different register and with a narrower range.
すら vs さえ: same job, different register
大辞泉 (副助 すら) gives sense 1 as 「極端な事を例としてあげ、他を類推させる意を表す。さえ。でも。…でさえ。」(cite an extreme case to make one infer the rest; equals さえ, でも, …でさえ).5 So すら's core meaning is さえ's scalar "even." The difference is register: すら is the more formal, literary equivalent. Tofugu, citing Janet Ashby, calls すら "a more literary equivalent of さえ" and notes it probably sounds highbrow when spoken.7
子供ですら計算できる。5
"Even a child can do the calculation."
喉が痛くて、水すら飲めない。10
"My throat hurts so much I can't even drink water."
この悩みは家族にすら言えない。10
"I can't talk about this worry even to my family."
The history explains the register. 大辞泉's usage note records that すら was frequent in 上代 (Old Japanese), declined after the medieval period in favor of さえ, and now appears chiefly in formal, poetic, or classical-flavored contexts.5 After a noun, ですら is the formal counterpart of でさえ, and にすら parallels にさえ.10
What すら cannot do: the さえ〜ば boundary
Here is the key contrast. The conditional "if only / as long as" sense belongs to さえ: Tofugu notes that when さえ is followed by a conditional it means "only", as in 君さえいれば.7 すら is the literary scalar equivalent of さえ,7 but it carries only the scalar-focus sense. It does not carry that conditional use.
Concretely, さえ allows これさえすれば ("as long as you do this"), but the parallel すら〜ば is not a standard construction. A learner who has internalized すら as "just a fancier さえ" may try to slot it into a conditional and produce something ill-formed. The swap does not work in that direction.
すら〜ない: stacking with negation
すら very often pairs with a negative to mark "not even the minimum", the 最低限 (minimum-limit) reading.7 大辞泉's sense 2 captures why the pairing is natural: 「『すら』を伴う語からは、ふつう、考えられない、またはあってはならないようなことが起こる意を表す」(it indicates that something normally unthinkable or impermissible occurs).5 In everyday use, すら often appears as an unthinkable case stated in the negative.
彼女は自分の名前すら書く事が出来ない。7
"She can't even write her own name."
こんな問題、小学生すらわかるよ。10
"A problem like this? Even an elementary schooler gets it."
すら is not negation-only: the dictionary's own headword example is affirmative (子供ですら計算できる).5 But すら〜ない is its highest-frequency live use, so it is the pattern to recognize first.710
だに: the archaic/literary "even"
だに is the particle that modern prose rarely touches, and it behaves least like the others. You meet it when reading, not when composing new sentences.
A frozen classical particle, not a productive one
だに is a classical (古語) 副助詞 (adverbial particle). 学研『全訳古語辞典』 records two senses. The first is a 最小限 (minimum-limit) sense, 「せめて…だけでも。せめて…なりとも」(at the very least, even if only), used with commands, wishes, and intent. The second is a 類推 (inference) sense, 「…だって。…でさえ。…すら」(even; even as much as), appearing with negation.11
Its history explains why the modern use is so narrow. 大辞泉's usage note reads 「上代では①が主で、②は『すら』の領域であったが、平安時代には多く打消しの表現と呼応する形で『すら』の領域をも兼ねるようになった」(in 上代 sense ① dominated and the "even" sense ② belonged to すら's territory; in the Heian period だに came to cover すら's territory too, largely in concord with negation).6 だに was the Heian-period "even" particle. In the medieval period, さへ later displaced it.611
For learners, the takeaway is simple: だに is not productive. It survives only in fixed, idiomatic expressions; you recognize it, you do not freely form new phrases with it.89 Its register is classical and literary: a 古語 (classical-language) particle that survives as 古い表現 (old-fashioned expressions) in set phrases.119
The two survival patterns
だに lives on in two common collocation patterns.
The first is verb-dictionary-form + だに, "even just (doing X)", in affirmative sentences. Just doing the action is enough to produce the result. Dictionary-confirmed collocations include 想像するだに, 考えるだに, 聞くだに, and 見るだに.89
想像するだに恐ろしい。8
"It is terrifying even just to imagine it."
The second is noun + だに〜ない, an emphatic total negation: "does not even ~ in the slightest." The reliably attested collocations are 微動だにしない and 一顧だにしない.1213
想像だにしませんでした。8
"I never even imagined it."
大辞泉 lists 微動だにしない under 微動 (「かすかに動くこと。『微動だにしない』」), with the meaning "does not move even slightly, does not budge at all."12 For 一顧だにしない the gloss is 「わずかに振り返ってみることもしない。まったく顧みない」(does not so much as glance back; takes no notice whatsoever).13
The minimum-limit sense ① appears in classical sources. It is useful only as an illustration of the origin.
That line is from 竹取物語 (The Tale of the Bamboo Cutter), cited in 大辞泉 and 学研全訳古語辞典 as the 最小限 sense.611 It is Classical Japanese. Read it as history, not as a model for modern composition.
Choosing between them: a decision map
Once each particle is clear, the choice comes down to one prior check and one register decision.
The register ladder: さえ → すら → だに
The three scalar particles share the scalar "even" meaning and differ by register. The dictionaries establish each rung independently. さえ is the neutral default, spoken and written, and the only one carrying the さえ〜ば conditional;4 すら is "a more literary equivalent of さえ", with the same scalar job;57 だに is 古語, not productive, and alive only in set phrases.61189
No single high-tier source states the full three-way ranking in one line. The ladder is this article's synthesis of three independent register notes, each sourced above.
A side-by-side view makes the trade-offs clear.
| Particle | Scalar "even"? | Register | Conditional (〜ば)? | Productive today? |
|---|---|---|---|---|
| さえ | yes | neutral (spoken + written)4 | yes (さえ〜ば)4 | yes |
| すら | yes | formal / written / literary57 | no | yes (esp. すら〜ない)10 |
| だに | yes (cl. 類推)11 | archaic / frozen-literary611 | no | no (set phrases only)89 |
| こそ | NO (identification)3 | neutral, affirmative3 | n/a | yes |
And こそ is a different question entirely
If you mean "exactly this one, this is the very one", reach for こそ. It is not on the scalar ladder at all. It identifies and emphasizes which element, rather than citing an extreme case for inference.63
One family note helps place these particles in the wider system. も is the "also / even" base the scalar particles build on, which is why さえも and すらも attach も. でも and まで sit in the same とりたて family and overlap with the scalar "even" zone (でも "even / at least", まで "even / to the extent").12
Good to know
Pitfall: you cannot swap すら into a さえ〜ば conditional
The most common error in this family is treating すら as a drop-in replacement for さえ everywhere, including the さえ〜ば "if only" conditional. すら carries only the scalar-focus "even" sense. It does not enter that conditional. さえ alone covers both the scalar focus and the sufficient-condition "if only" use.7
A learner reaching for "as long as I have just this, I can pass" might write これすらあれば、合格できる. That form is deliberately ill-formed here: すら does not take the conditional. The correct form uses さえ. The sentence is constructed for this contrast.
これさえあれば、合格できる。
"As long as I have just this, I can pass."
Etymology aside: だに and the classical roots of the "even" particles
The "even" particles developed in historical layers. In 上代 (Old Japanese), すら carried the scalar "even". In the Heian period, だに expanded to cover that territory, largely in concord with negation. In the medieval period, さへ (modern さえ) took over and remains the everyday form.611
The modern register ladder therefore mirrors the order in which each particle was most current: さえ everyday, すら formal, だに frozen. だに's surviving set phrases (微動だにしない, 想像するだに) are fossils of its Heian-era productivity.68
Mnemonic: the formality dial
Picture one dial turned toward formality: これさえ (casual), これすら (formal), 微動だに (frozen). It is the same "even" meaning, with three settings on a single register dial. Pick by how formal or literary the context is. This is a memory hook synthesizing the sourced register ladder above, not a quoted source.
See also
- The しか Particle: Only (with Negative)
- The だけ Particle: Only (Limit)
- The なんて / なんか Particles: Dismissive Listing
- The くらい / ぐらい Particle: Approximation and "About"
- The など Particle: Etc., Such Things As
- The は Particle: Topic Marker