Start with a question:
田中さんはもう来た＿＿です。さっき電話がありましたから。
A. はず B. そう C. よう D. らしい
The answer is A. はず. "Tanaka should have arrived already -- there was a phone call earlier." はず expresses a conclusion based on evidence.
The Core Feeling of はず
はず expresses a reasoned expectation -- the speaker has grounds to believe something should be true, but hasn't confirmed it yet:
| Example | Meaning |
|---|---|
| 田中さんは来るはずです。 | Tanaka should come. (I have reason to think so) |
| 財布はカバンにあるはずです。 | My wallet should be in my bag. (I remember putting it there) |
| もう届いたはずです。 | It should have arrived. (Based on the timing) |
The key to はず: the speaker has evidence (an agreement, experience, calculation) -- it's not a random guess.
Conjugation Rules
| Word type | How to attach | Example |
|---|---|---|
| Verb | Plain + はず | 来るはず, 来たはず |
| い-adjective | Plain + はず | 安いはず, 高かったはず |
| な-adjective | Stem + な + はず | 元気なはず, 静かなはず |
| Noun | Noun + の + はず | 休みのはず, 日曜日のはず |
な-adjectives use な, nouns use の -- because はず is itself a noun.
はず vs Other Conjecture Expressions
| Expression | Feeling | Basis |
|---|---|---|
| はず | Should be (reasoned expectation) | Concrete evidence |
| だろう | Probably (guess) | Personal judgment |
| かもしれない | Maybe (possibility) | Uncertain |
| そうだ (様態) | Looks like (appearance) | What's in front of you |
| らしい | Apparently / seems like | Hearsay or indirect evidence |
はず has the highest certainty level, just below "definitely."
Negative Forms
はずがない = Can't Possibly Be
Expresses "based on my reasoning, this is impossible":
-
そんなことがあるはずがない。 → There's no way that could happen.
-
彼が嘘をつくはずがない。 → He can't possibly be lying.
ないはず = Shouldn't Be
Expresses "I expect this won't happen":
-
田中さんは来ないはずです。 → Tanaka shouldn't be coming.
-
まだ届いていないはずです。 → It shouldn't have arrived yet.
はずがない (impossible) is stronger than ないはず (shouldn't).
When Expectations Fail: はずだったのに
When reality doesn't match the expectation, use はずだったのに:
-
5時に届くはずだったのに、まだ届かない。 → It was supposed to arrive at 5, but it still hasn't.
-
今日は休みのはずだったのに、仕事が入った。 → Today was supposed to be my day off, but work came up.
Self-Test
Q1. What's the difference between 「もう届いたはずです」 and 「もう届いたでしょう」?
Show answer
- はず → Based on evidence (e.g., checked the tracking, calculated the timing)
- でしょう → Personal guess ("I think it probably arrived")
はず is more confident; でしょう is more vague.
Q2. Fill in: 彼女は元気＿＿はずです。
Show answer
な. な-adjectives use な to connect to はず: 元気なはずです.
Q3. What does 「彼が犯人のはずがない」 mean?
Show answer
"He can't possibly be the culprit." Noun 犯人 + の + はずがない expresses strong denial -- based on my reasoning, this is absolutely impossible.
Summary
- はず = "should be" -- a reasoned expectation with evidence
- Conjugation: plain form + はず (な-adjectives use な, nouns use の)
- はずがない = can't possibly be (strong denial)
- ないはず = shouldn't be (mild denial)
- はずだったのに = was supposed to... but... (failed expectation)
- Compared to だろう/かもしれない: はず is the most confident