Expressing "just now" with 刚, 刚 and 刚刚
The adverbs 刚才, 刚 and 刚刚 have similar meanings, but differ on a few key uses.
The adverb 刚
刚 
emphasizes that the action happened a short time ago.
刚 is placed before a predicate expressed by a verb or adjective.
emphasizes that the action happened a short time ago.
刚 is placed before a predicate expressed by a verb or adjective.Scheme
刚
predicate
Examples
我刚买的那些饼干在哪儿？
Where are the cookies I just bought?
wǒ gāng mǎi de nàxiē bǐnggān zài nǎr
天刚黑他就意识到已经太晚了
As soon as it got dark, he realized it was too late
tiān gāng hēi tā jiù yìshídào yǐjīng tài wǎn le
There may be a word in front of 刚 to indicate the time: today, tonight, last month.
Examples
人家今天刚来了，别打扰他
He just arrived today, don't bother him
rénjiā jīntiān gāng lái le, bié dǎrǎo tā
刚 can also be accompanied by a specific time, to show the time between when the action happened and now.
Scheme
刚
verb
(object)
whom?/where?
duration
how long?
Examples
他刚来了一天，还没有朋友
He arrived just one day ago, so he has no friends yet
tā gāng lái le yì tiān, hái méi yǒu péngyou
我刚到超市五分钟
I just got to the shop five minutes ago
wǒ gāng dào chāoshì wǔ fēnzhōng
Placing 刚 before adjectives can have a meaning: "just right”.
Examples
大小刚合适，不大也不小
The size is just right, not too big or small
dàxiǎo gāng héshì, bú dà yě bù xiǎo
In negative forms, 刚 is only used with 不是 . It cannot be used with 没 .
. It cannot be used with 没 .Examples
我不是刚出生的
I wasn't born yesterday
wǒ bú shì gāng chūshēng de
不是昨天刚买的吗？怎么已经丢了呢？
Didn't you just buy it yesterday? How did you manage to lose it already?
bú shì zuótiān gāng mǎi de ma? zěnme yǐjīng diū le ne
The adverb 刚刚
刚刚 is used in the same way as 刚, but indicates a shorter period of time.
is used in the same way as 刚, but indicates a shorter period of time. Pay attention
"A short time ago" is relative and depends on the speakers‘ subjective feeling. For this reason, 刚 and 刚刚 can indicate that something happened 1 minute ago, or even a year ago.
Examples
刚刚来就走
You’ve just arrived but are already leaving
gānggāng lái jiù zǒu
我昨天刚刚出去的
I just went out yesterday
wǒ zuótiān gānggāng chūqù de
刚刚 can be also used with adjectives in the sense of "just right”.
Examples
我们来了刚刚好，电影还没开始呢
We arrived just in time, the film hadn't started yet
wǒmen lái le gānggāng hǎo, diànyǐng hái méi kāishǐ ne
The adverb 刚才
刚才 emphasizes that the action took place quite recently, and the time elapsed is really short.
emphasizes that the action took place quite recently, and the time elapsed is really short. Pay attention
刚才 expresses that the time elapsed is really short — we're talking no more than 1-30 minutes in most situations.
刚才 can be placed before a verb or a subject.
Examples
你猜我刚才见到谁了
Guess who I just met
nǐ cāi wǒ gāngcái jiàndào shéi le
刚才她还在这儿
She was just here
gāngcái tā hái zài zhèr
根据你刚才所说的，我不明白怎么会产生那样的结果
Based on what you just said, I don't understand how it could have happened
gēnjù nǐ gāngcái suǒ shuō de, wǒ bù míngbai zěnme huì chǎnshēng nàyàng de jiéguǒ
In negative sentences we use either 没 or 不 after 刚才.
or 不 after 刚才.Examples
为什么你刚才不告诉我水这么热呢?
Why didn't you just tell me the water was so hot?
wèishénme nǐ gāngcái bú gàosu wǒ shuǐ zhème rè ne
奇怪的是我刚才没注意到这扇门
It' strange that I didn't notice this door just now
qíguài de shì wǒ gāngcái méi zhùyìdào zhè shànmén
刚才 can be used as an adjective to modify a noun, whereas 刚 and 刚刚 can not. Just add 的 after 刚才.
after 刚才.Examples
我们能从刚才的部分继续吗？
Can we pick up where we left off?
wǒmen néng cóng gāngcái de bùfen jìxù ma
他把刚才的事儿忘了
He forgot what happened just a moment ago
tā bǎ gāngcái de shìr wàng le