Usage note
昨天用来表示过去的一天，通常是前一天。
zuótiān yòng lái biǎoshì guòqù de yī tiān, tèbié shì kěnéng de qianyītiān。
昨天 is used to indicate a past day, usually the previous day.
Context note
昨天常用于描述前一天发生的事情，比如上学、吃饭等日常活动。
zuótiān cháng yòng yú miáo shù qianyītiān fāshēng de shìqíng, bǐrú shàngxué、chǎnfàn děng rìtānghuó。
昨天 is often used to describe events from the previous day, such as going to school or eating meals.
5 examples
昨天我去了公园。
zuó tiān wǒ qù le gōng yuán。
Yesterday I went to the park.
昨天妈妈做了蛋糕。
zuó tiān mā ma zuò le dàn gāo。
Mom made a cake yesterday.
昨天我们去图书馆了。
zuó tiān wǒ men qù tú shū guǎn le。
We went to the library yesterday.
昨天天气很好。
zuó tiān tiān qì hěn hǎo。
The weather was very good yesterday.
昨天我和朋友一起吃饭。
zuó tiān wǒ hé péng yǒu yì qǐ chī fàn。
Yesterday I had dinner with my friends.
5 mini stories
昨天我吃了冰淇淋，很好吃。昨天晚上我们看了电影。
zuó tiān wǒ chī le bīng qí lín， hěn hǎo chī。 zuó tiān wǎn shàng wǒ men kàn le diàn yǐng。
I ate ice cream yesterday, it was very delicious. We watched a movie last night.
昨天我和爸爸去了超市，买了很多东西。昨天下午我们在公园玩得很开心。
zuó tiān wǒ hé bà ba qù le chāo shì， mǎi le hěn duō dōng xī。 zuó tiān xià wǔ wǒ men zài gōng yuán wán dé hěn kāi xīn。
Yesterday I went to the supermarket with Dad and bought many things. Yesterday afternoon we had fun in the park.
昨天我学了新单词，很开心。昨天晚上我们吃了火锅。
zuó tiān wǒ xué le xīn dān cí， hěn kāi xīn。 zuó tiān wǎn shàng wǒ men chī le huǒ guō。
Yesterday I learned new words, I was very happy. We had hotpot last night.
昨天我和妹妹一起去了动物园，看到了很多动物。昨天下午我们在家看书。
zuó tiān wǒ hé mèi mei yì qǐ qù le dòng wù yuán， kàn dào le hěn duō dòng wù。 zuó tiān xià wǔ wǒ men zài jiā kàn shū。
Yesterday my sister and I went to the zoo and saw many animals. Yesterday afternoon we read books at home.
昨天我们全家一起去爬山了，很累但很开心。昨天晚上我们一起吃了晚饭。
zuó tiān wǒ men quán jiā yì qǐ qù pá shān le， hěn lèi dàn hěn kāi xīn。 zuó tiān wǎn shàng wǒ men yì qǐ chī le wǎn fàn。
Yesterday our whole family went hiking, it was tiring but very fun. We had dinner together last night.
Mini dialogue
昨天天气
A
昨天天气怎么样？
Zuótiān tiānqì zěnme yàng?
How was the weather yesterday?
B
昨天下雨了，很冷。
Zuótiān xià yǔ le, hěn lěng.
It rained yesterday, very cold.
昨天作业
A
你昨天做作业了吗？
Nǐ zuótiān zuò zuòyè le ma?
Did you do your homework yesterday?
B
做了，昨天我写了汉字。
Zuò le, zuótiān wǒ xiě le Hànzì.
Yes, I wrote Chinese characters yesterday.
Related words and contrasts
contrast
今天
jīntiān
today
今天 means the current day, while 昨天 means the day before.
contrast
明天
míngtiān
tomorrow
明天 means the day after today, opposite to 昨天.
related
前天
qiántiān
the day before yesterday
前天 is two days before today, one day earlier than 昨天.