就【jiù】

就 goes before the verb and ties the action to something before it – a time, another action, a condition. Its two commonest jobs are "then, straight after" and "as early as".

"Then", straight after

就 between two actions says the second follows the first with no delay. The first often carries 了.

Earlier or easier than expected

A time word or an amount before 就 says it happened sooner, faster or more easily than you'd think. The sentence ends in 了.

就 always goes after the time word and the subject, right before the verb.

• × 他就六点起床了 → 他六点就起床了
• × 就他六点起床了 → 他六点就起床了

The opposite – later or harder than expected – is 才, and 才 drops the 了.

就在 "right there"

就在 + place points at a spot: "right there", "just over there".

就 also closes 如果…就 "if … then" and 一…就 "as soon as", which have their own points.