“〜hazu da / hazu ga nai”: Grounded Expectation and Its Negation [JLPT N4]
Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026
「9時に来るはずだ」「そんなはずがない」 — two uses in one go.
「この電車は6時に着くはずだ」 — a grounded “should”
「時刻表で調べたから、6時に着くはずだ」 (I checked the timetable, so it should arrive at 6) — 「はず」 expresses a grounded, reasoned inference, with two uses: 〜はずだ = (by reason) should ~ (inferred from facts or common sense); 〜はずがない = can't possibly ~, surely not (a negative inference). Its confidence is higher than 「でしょう／かもしれない」 — not an offhand guess, but “I have reason to think so.” This guide covers はず's uses, attachment, and its place on the confidence scale.
Core: a reasoned inference from grounds
「はず」 = “from some basis (fact, common sense, experience), it should be so”:
- 〜はずだ = should ~, ought to ~: 彼は約束したから、来るはずだ (he promised, so he should come).
- 〜はずがない = can't possibly ~ (strong negation): 彼が嘘をつくはずがない (he can't possibly be lying).
Key: there are grounds (≠ an offhand guess). So its confidence beats かもしれない and でしょう.
Uses / attachment
| Use | Attachment | Example |
|---|---|---|
| 〜はずだ (positive inference) | plain form／noun の／na-adj な | 着くはずだ |
| 〜はずがない (negative inference) | same | あるはずがない （there's no way it exists） |
| noun ＋ の ＋ はず | noun attachment | 休みのはず |
Example sentences
- この電車は6時に着くはずだ。(This train should arrive at 6.) — grounded inference
- 彼が嘘をつくはずがない。(He can't possibly be lying.) — strong negation
- 彼女はもう着いているはずだ。(She should have arrived by now.) — inference
- 今日は休みのはずだ。(Today should be a day off.) — noun ＋ の
- そんな高い店、学生が行けるはずがない。(A place that pricey — a student can't possibly afford it.) — negative inference
⚠️ Where learners slip up
① Attachment: noun ＋ の ＋ はず, na-adj ＋ な ＋ はず. 休みのはず (✗ 休みはず), 静かなはず (✗ 静かはず). Verbs and i-adjectives attach directly in plain form (着くはず, 高いはず).
② はず (grounded) vs かもしれない (unsure). 「来るはず」 = I have reason to think they'll come (high confidence); 「来るかもしれない」 = they might come (unsure). Don't mix grounded はず with offhand かもしれない.
③ 「はずがない」 = strong negation “can't possibly.” Not “probably not,” but “surely can't” (そんなはずがない = it can't possibly be so). Stronger than 「ないでしょう」.
🔄 Compare: the confidence spectrum
| Form | Confidence／nuance | Example |
|---|---|---|
| 〜かもしれない | low (maybe) | 来るかもしれない （might come） |
| 〜でしょう | mid (probably) | 来るでしょう |
| 〜はずだ | high (grounded, ought to) | 来るはずだ |
| 〜にちがいない | very high (definitely) | 来るにちがいない （must be coming） |
💡 Learning tip
The key to 「はず」 is “there are grounds” — it's not an offhand guess (that's かもしれない), but “from some fact/common sense, it ought to be so” (checked the timetable, so 6時に着くはず). On the confidence spectrum: かもしれない (maybe) ＜ でしょう (probably) ＜ はず (grounded, ought to) ＜ にちがいない (definitely). Also, 「はずがない」 is a strong negation “can't possibly” (嘘をつくはずがない = he surely can't be lying). Remember the attachment — noun ＋ の, na-adj ＋ な — and はず is solid.
❓ Quick FAQ
Q: 「はずだ」 vs 「かもしれない」?
By grounds and confidence. 「はずだ」 is a grounded inference (by reason it should ~, high confidence: 時刻表で調べたから6時に着くはずだ); 「かもしれない」 is an unsure guess (maybe ~, low confidence: もしかしたら来るかもしれない). Reason to think so → はず, a mere possibility → かもしれない.
Q: What does 「はずがない」 mean?
A strong negation “can't possibly, surely won't” (a negative inference): 彼が犯人のはずがない = he can't possibly be the culprit. Much stronger than 「〜ないでしょう (probably won't)」, expressing a confident “it surely can't be so.” Note the attachment: noun ＋ の ＋ はずがない (犯人の はずがない).
🖊️ Practice Quiz
Q1. 「この電車は6時に着く___。」(should arrive at 6 — per the timetable)
(A) でしょう (B) はずだ (C) にちがいない (D) だろう
Q2. 「彼が嘘をつく___。」(there's no way he'd lie)
(A) はずだ (B) でしょう (C) はずがない (D) わけだ
Q3. 「彼女は___はずだ。」(she should be busy)
(A) 忙しい (B) 忙しな (C) 忙しの (D) 忙しく
Q4. 「今日は休み___はずだ。」(today should be a day off — noun)
(A) だ (B) な (C) の (D) に
Q5. 「映画は8時に始まる___だったのに、9時だった。」(should have started at 8, but it was 9)
(A) でしょう (B) はず (C) にちがいない (D) かもしれない
Answer Key
1. (B) はずだ ── with a timetable as grounds and high certainty, use はずだ; でしょう has weaker grounds.
2. (C) はずがない ── ‘no way he'd lie' uses the negative はずがない. はずだ is the positive ‘should.'
3. (A) 忙しい ── an い-adjective plain form ＋ はず: 忙しいはず.
4. (C) の ── a noun ＋ の ＋ はず: 休みのはず.
5. (B) はず ── 「はずだったのに」 = should have …, yet (fallen-through expectation): 始まるはずだったのに.