就 and 才 (Then/Only then)

就 (jiù) and 才 (cái) are two adverbs that express the speaker's attitude about timing or conditions. They both go before the verb, but they carry opposite connotations. Understanding this contrast is key to using them correctly.

就 implies that something happens sooner than expected, quickly, easily, or without much effort. "他六点就起床了" — "He got up at 6 o'clock already (early!)." The speaker feels 6 AM is early. 就 often pairs with 了 at the end of the sentence because the action has already been completed (sooner than expected).

才 implies that something happens later than expected, with difficulty, or only under certain conditions. "他十点才起床" — "He didn't get up until 10 o'clock." The speaker feels 10 AM is late. Note: 才 does NOT pair with 了. Since 才 already conveys the sense that something finally happened (after a long wait), 了 is unnecessary and sounds unnatural.

Compare: "他八点就来了" (He came at 8 — that's early!) vs. "他八点才来" (He didn't come until 8 — that's late!). The clock time is the same, but the speaker's feeling is completely opposite. This subjective nature of 就 and 才 is what makes them so expressive and important in Chinese.