Usage note
“不久”表示时间很短，很快会发生或刚刚发生。
“bù jiǔ” biǎoshì shíjiān hěn duǎn, hěn kuài huì fāshēng huò gānggāng fāshēng.
It means a short time, used to say something will happen soon or just happened a little while ago.
Context note
不久用来表示时间很短，很快会发生或刚刚发生。它属于时间话题。
bù jiǔ yòng lái biǎo shì shí jiān hěn duǎn, hěn kuài huì fā shēng huò gāng gāng fā shēng. tā shǔ yú shí jiān huà tí.
不久 is used to say that something will happen soon or just happened a short time ago. It belongs to the topic of time.
5 examples
不久，他妈妈回来了。
bù jiǔ， tā mā ma huí lái le。
不久，他妈妈回来了。 (Not long after, his mother came back.)
他们很快结婚了，不久就有了孩子。
tā men hěn kuài jié hūn le， bù jiǔ jiù yǒu le hái zi。
They got married quickly and soon had a child. (They got married quickly, not long after they had a child.)
他刚搬进新家，不久就认识了很多邻居。
tā gāng bān jìn xīn jiā， bù jiǔ jiù rèn shi le hěn duō lín jū。
He just moved into his new home, not long after he met many neighbors. (He just moved into his new home, not long after he got to know many neighbors.)
他生病了，不久医生来了。
tā shēng bìng le， bù jiǔ yī shēng lái le。
He was sick, and soon the doctor came. (He was sick, not long after the doctor arrived.)
他们去旅行，不久就拍了很多照片。
tā men qù lǚ xíng， bù jiǔ jiù pāi le hěn duō zhào piàn。
They went on a trip, and soon took many photos. (They went on a trip, not long after they started taking lots of pictures.)
5 mini stories
小明生病了，不久医生来了。小明的妈妈很担心。
xiǎo míng shēng bìng le， bù jiǔ yī shēng lái le。 xiǎo míng de mā ma hěn dān xīn。
Xiao Ming was sick, and soon the doctor came. Xiao Ming's mother was very worried. (Xiao Ming was sick, not long after the doctor arrived. Xiao Ming's mother was very worried.)
他们去公园玩，不久就看到了美丽的花。
tā men qù gōng yuán wán， bù jiǔ jiù kàn dào le měi lì de huā。
They went to the park to play, and soon saw beautiful flowers. (They went to the park to play, not long after they saw some lovely flowers.)
小红刚搬进新家，不久就认识了很多邻居。她很高兴。
xiǎo hóng gāng bān jìn xīn jiā， bù jiǔ jiù rèn shi le hěn duō lín jū。 tā hěn gāo xìng。
Xiao Hong just moved into her new home, and soon got to know many neighbors. She was very happy. (Xiao Hong just moved into her new home, not long after she met lots of new neighbors. She was very happy.)
他们去旅行，不久就拍了很多照片。他们很开心。
tā men qù lǚ xíng， bù jiǔ jiù pāi le hěn duō zhào piàn。 tā men hěn kāi xīn。
They went on a trip and soon took many photos. They were very happy. (They went on a trip, not long after they started taking lots of pictures. They were very happy.)
小华生病了，不久医生来了。他的妈妈很担心。
xiǎo huá shēng bìng le， bù jiǔ yī shēng lái le。 tā de mā ma hěn dān xīn。
Xiao Hua was sick and soon the doctor came. His mother was very worried. (Xiao Hua was sick, not long after the doctor arrived. His mother was very worried.)
Mini dialogue
不久就回来
A
妈妈不久就回来。
Māma bù jiǔ jiù huílái.
Mom will be back not long after.
B
好的，我在这里等她。
Hǎo de, wǒ zài zhèlǐ děng tā.
Okay, I'll wait for her here.
不久放假
A
不久就要放假了。
Bù jiǔ jiù yào fàngjià le.
Not long after, we'll be on holiday.
B
我很期待！
Wǒ hěn qīdài!
I'm looking forward to it!
Related words and contrasts
similar
一会儿
yíhuìr
a short while
不久 and 一会儿 both refer to a short time.
opposite
很久
hěn jiǔ
a long time
不久 means soon; 很久 means a long time.