The two adverbs are used to express that events have occurred earlier, faster or later, slower than the speaker expected. This is the use we’re going to see here.
就 and its opposite 才
Both 就 and 才 can be used after a word or phrase expressing time. 就 is placed before a verb to show the speaker thinks the action took place earlier, sooner, faster or lasted for a briefer time than expected. Also placed before a verb,才 is the complete opposite. 才 suggest actions that were accomplished later, more slowly or took longer than expected by the speaker. Let’s see how each one works.
Using 就
Earliness with 就
就 can be used to express feelings of earliness: it shows the speaker feels the action is happening sooner than expected. In such situations, 就 can be translated into “as early as” or “as quickly as”, but it’s often not specifically indicated when translated.
To know: When 就 is used in this way, the sentence usually ends with the particle 了 to mark the completed action. 就 is also usually preceded by a time word, such as a specific time or age.
For example, your friend usually has dinner at 5 pm, which you find is a really early time to have dinner. You can use 就 and say:
我的朋友每天五点就吃完 饭 了。
My friend eats dinner (as early as) at 5pm everyday.
Structure
Subject + Time + 就 + Verb
Examples
夏天五点多天就亮 了。
During the summer, the sun rises as early as 5 a.m.
昨天早上我五点半就起床 了。
I got up at 5.30 a.m yesterday.
Actions that were faster, or lasted for a shorter time than expected with 就
就 is the word you use when you want to express the feeling that you think that the action that took place happened too briefly or the time since the action started or happened is too short. 就 is often preceded by time periods in such sentences.
就 shows your surprise, the unexpectedness of the situation, or even regret. For example, your friends came to visit you but they only stayed for a few hours. You feel sad and you want them to stay longer. In situations like these, you can use 就 to express that.
你们怎么才来就要 走？
You just arrived! Why you are leaving so soon?
Structure
就+Verb
Examples
我昨晚很早就睡觉 了。
I went to sleep very early last night.
你们 这么 早 就 回家 了？
Why are you back already?
Using 才
When talking about time, 才 is the word you use to either express a feeling of lateness, or a feeling of an action taking longer than expected.
Expressing lateness
才 is useful to express that you think an action took place later than expected. It can usually be translated as “not until” or “as late as” in English. Here, 才 is often used with a time number of some sort, such as a specific time or a specific age.
Yocha, for instance, would use 才 to show Nincha he feels he got up really late. He’d say:
现在 已经 十二 点, 你怎么才起床？
It’s 12 p.m already, How are you only getting up now?
Structure
Subject + Time +才+ Verb + Object
Examples
电影 七 点 开始，他七点十分才来，迟到了。
The movie started at 7, he arrived at 7:10 and was late.
他 结婚 的 时候才四十 岁。
It wasn’t until he was forty that he got married.
To know: Sentences using 才 in this way should not end with 了 as they do not convey a sense of completion.
Expressing actions that took longer than expected with 才
才 is also a word you can use when you want to show that you think the action lasted longer or took place more slowly than expected. In such sentences, 才 will often be placed after time periods.
For example, your friend is late and you had to wait an hour for them. In this situation, you’ll want to use 才 to show you found they took a good long while to show up. Here’s what you could say to them:
我等了你一个小时你才来。
I waited for an hour for you before you (finally) arrived.
Structure
才+Verb
Examples
爸爸怎么这么晚_才_下班？
Why did Dad get off work that late?
我想了半天_才_明白。
It wasn’t until I thought about it a long time that I understood.
Watch your tone: In sentences like this, 才 tends to denote anxiety, impatience, anger, and so on.
On an end note, a little something to ponder: Feeling that an action is early or late, takes longer or less than expected is highly subjective, and there’s no uniform standard. You’ll have to learn and remember to keep an open mind when these two adverbs are concerned.