該 — the bare, condensed form of 應該, often negated as 不該 (ought not).

TSUMUGU · TBCL 4 (est.) · 語法

該 grammar point · tier 1 · 該 — modal of advisability (should / ought to), the bare form

· gāi

Auxiliary before a verb: marks the action as the fitting thing for the subject to do (should, ought to) — the bare, condensed form of 應該, often negated as 不該 (ought not).

Hook inherited from 應該.

Auxiliary before a verb

框 · Frame

[subj] (不)該 [verb phrase]

觸 · Trigger

You are saying an action is the fitting thing for the subject to do, and you want it said short — often as the ought-not 不該.

序 · The move

1name the subject the action falls to

2set 該 directly before the verb phrasedoes 該 sit in front of a verb, not a noun?

3confirm the bare 該 fits the register; 應該 is the fuller everyday form for the same shouldis the short 該 wanted here, or would 應該 read more naturally?

4negate as 不該 (ought not), placing 不 before 該did you put 不 in front of 該, not negate the verb alone?

例 · Examples

1我們we平常ordinarily / usually不該吃eat太鹹too salty的attributive: modifier to noun食物food。

We ordinarily should not eat food that is too salty.

界 · Boundary

應該

該 and 應該 name the same should. 該 is the bare, condensed form, terser and a touch more written, and shows up readily as the negated 不該. 應該 is the fuller everyday word. Use 該 for the short, set 應該 where a complete two-syllable modal reads more naturally.

不用／不必

不該 says the action is the wrong thing to do (you ought not). 不用／不必 says the action is unneeded (you may skip it). 不該吃 — ought not eat it; 不用吃 — no need to eat it. One judges the act wrong, the other releases you from doing it.

noun after 該: 你該水 → 你該喝水（該 + verb）

negating the verb instead of the modal: 該不吃 → 不該吃（不 goes before 該）

ought-not read as need-not: 不該帶 misread as 'no need to bring' → it means 'ought not bring'; for 'no need' use 不用／不必帶

English 'should' and 'shouldn't' map onto 應該/該 cleanly, but learners reaching for one syllable often drop 應 and then stall on negation, writing 該不 on the A-not-A model rather than 不該; some also blur 不該 (ought not) into 不用 (need not).