Usage note
快乐可以用来形容人们的心情,比如在节日、生日或者和朋友一起玩的时候。
kuài lè kě yǐ lái yòng de míng jīng, bǐ 如 在 jié rì、shēng rì huò zhě ér qiě yǔ péng yǒu yī qǐ wán de shí hòu。
快乐 can be used to describe people's moods, such as during festivals, birthdays, or when playing with friends.