欢乐 is commonly used in both written and spoken Chinese, though it carries a slightly more formal or descriptive tone than the everyday word `开心 (kāixīn)`.
Describing Events and Atmospheres: It's perfect for describing holidays, parties, festivals, and performances. For example, “a joyful festival” (欢乐的节日) or “the scene was filled with a joyful atmosphere” (现场充满了欢乐的气氛).
Describing Time Periods: It's often used to characterize a happy period of time, such as one's childhood (欢乐的童年) or a vacation (欢乐的时光, “joyful times”).
In Media and Branding: The word is very popular in marketing and media to evoke positive feelings. You'll see it in song titles, TV show names, and slogans for amusement parks, like the famous “Happy Valley” (欢乐谷 Huānlè Gǔ) chain in China.
As a Noun: It can also act as a noun meaning “joy” or “merriment.” For example, “to bring joy to everyone” (给大家带来欢乐).