應該grammar point · tier 1 · 應該 — modal of advisability (should / ought to)
· yīnggāi
Auxiliary before a verb: marks the action as the fitting thing to do — what the situation calls for and what falls to the subject (should, ought to).
字源 FORM what the parts do
應 sets a heart (心) under a falcon (鷹, its bird folded away, on loan for the sound yīng) — the heart that answers when the case calls. 該 sets speech (言) over 亥 (hài, on loan for the sound, worn from h to g); the speech is the full account, and what the full account assigns to you is what falls to you. Together before a verb, they name the action the situation calls for and lays at your feet.
故事 STORY a scene to remember it by
A bill lands on the table, and the heart already knows the share that falls to this one to settle.
字源記憶法
框 · Frame
[subj] 應該 [verb phrase]
觸 · Trigger
You are saying an action is the fitting, advisable thing for someone in this situation.
序 · The move
1name the subject the action falls to
2set 應該 directly before the verb phrasedoes 應該 sit in front of a verb, not a noun?
3confirm this is what the situation calls for, advisable rather than hard-requiredwould 要 / 必須 (a strict must) fit better than 應該?
4negate as 不應該 (ought not), placing 不 before 應該did you put 不 in front of 應該 rather than inside it?
例 · Examples
1運動exercise後after應該should / ought to (the fitting thing)把disposal: act on the definite object汗sweat擦乾wipe dry (verb + result)。
應該 names the fitting thing the case calls for, advice you can decline (你應該休息 — you ought to rest). 要 lays a hard requirement on the subject (你要休息 — you have to rest). 應該 recommends; 要 obligates.
應該 here is advisability — the right thing to do. 應該 also carries a likelihood reading (他應該到了 — he should be there by now), which 會 (probability) neighbours. The advisability sense sits before an action you choose; the likelihood sense estimates a fact.
negation inside the word: 應不該去 → 不應該去（不 goes before 應該）
noun after 應該: 你應該水 → 你應該喝水（應該 + verb）
strict requirement read as advice: 坐飛機應該繫安全帶 (sounds optional) → 坐飛機要繫安全帶 (a rule, use 要/必須)
English 'should' and 'must' feel close, so learners reach for 應該 where a hard rule needs 要/必須, softening an obligation into advice; some also negate as 應不該 on the model of A-not-A rather than 不應該.