副词：就

1. WHAT IT MEANS: 就 (jiù) is one of the most versatile adverbs in Mandarin. At HSK2, it has two primary uses: (a) expressing quickness or earliness — the action happens sooner than expected, right away, or at an earlier time than the listener imagined; (b) forming the result clause in a conditional "if...then" sentence.

2. USAGE 1 — RIGHT AWAY / SOONER THAN EXPECTED: Place 就 right before the verb. It always follows the subject and any time expression. Examples: 我八点就到了 (I arrived as early as 8 o'clock — earlier than expected); 他一听就懂了 (He understood the moment he heard it — immediately). Compare with 才 which means the opposite: later than expected.

3. USAGE 2 — CONDITIONAL (如果...就...): 就 appears in the result clause when a condition is introduced by 如果 (if), 要是 (if), or 只要 (as long as). Structure: 如果 + condition + 就 + result. Example: 如果你饿了，就去吃饭 (If you are hungry, then go eat).

4. PLACEMENT: 就 always comes BEFORE the main verb. It follows: subject > time word > 就 > verb. Never put 就 at the end of the sentence or before the subject.

5. 就 vs 才 — THE CRITICAL CONTRAST: 就 = earlier / sooner than expected → positive or neutral tone 才 = later / later than expected → implies dissatisfaction or surprise Example: 他八点就来了 (He came as early as 8 — we are impressed / relieved) vs 他八点才来 (He didn't come until 8 — we expected him earlier and are annoyed) The same time expression sounds early with 就 and late with 才, because it is all about the speaker's expectation.

6. 就 vs 已经: 已经 means "already" and often reports a completed fact. 就 focuses on the speed or earliness. Sometimes they overlap: 我已经到了 (I've already arrived — neutral) vs 我就到了 (I'll be there very soon). Do not treat them as synonyms.

7. COMMON MISTAKES: (a) Putting 就 after the verb: 他来就了 — wrong. 就 must come before the verb. (b) Using 就 when the action is late — use 才 instead. (c) Dropping 就 from the conditional result clause — this makes the sentence incomplete in formal Chinese.