As an imported art form, 歌剧 (gējù) occupies a specific niche in Chinese culture. It is generally perceived as a form of “high art” (高雅艺术, gāoyǎ yìshù), associated with sophistication, Western culture, and a certain level of education and affluence. Major cities like Beijing and Shanghai have world-class opera houses, such as the National Centre for the Performing Arts (国家大剧院), that stage both classic Western operas and modern Chinese-language operas composed in the Western style. The most important cultural distinction for a learner is between 歌剧 (gējù) and traditional Chinese opera, known collectively as 戏曲 (xìqǔ). The most famous type of 戏曲 is Peking Opera, or 京剧 (Jīngjù).
To an English speaker, this is like the difference between “Opera” and “Kabuki.” They are both forms of musical theater, but they are from vastly different cultural and aesthetic traditions. Using 歌剧 (gējù) to refer to 京剧 (Jīngjù) is a significant cultural mistake.
歌剧 (gējù) is used in both formal and informal settings when discussing the art form. People use it to talk about their interests, make plans, or discuss cultural events.
The term carries a neutral to positive connotation, implying a cultural and refined activity.