～はずだ

RuleVerb/adjective adnominal + hazu da: logical expectation, "it should / is bound to be" based on grounds.

Curiosity

How do you express grounded, logical confidence, as in "he should definitely come (since he promised)," in Japanese?

Intuition

hazu ("due course/reason") is the speaker's logical conclusion that "by reason it ought to be so." It is more confident than a mere guess (kamoshirenai), drawn naturally from grounds (a promise, rule, calculation). The denial is ~hazu ga nai ("can't possibly be").

Visualization

kuru → kuru hazu da (should come / is bound to). hazu da attaches to the adnominal (= verb dictionary form). For a past basis, ~ta hazu da (kita hazu da).

来るdictionary (adnominal)

Essence

Adnominal + hazu da. Verbs/i-adjectives attach directly (kuru hazu da, takai hazu da); na-adjectives use ~na hazu da (shizuka na hazu da); nouns use ~no hazu da (yasumi no hazu da). Strong negative reasoning is ~hazu ga nai. When expectations are betrayed, ~hazu datta noni is common.

Examples

約束したから、彼は来るはずです。

He promised, so he should come.

今日は日曜日だから、銀行は休みのはずだ。

It is Sunday, so the bank should be closed.

そんなに難しいはずがない。

It cannot possibly be that difficult.

Mini-quiz

Which fits "I bought a ticket, so I should be able to get in (logically)"? (haireru)