电灯泡 (diàn dēng pào) literally means “bulb” in Chinese. However, when people say “Don’t’ be a 电灯泡” to you, are they really asking you “not to be a bulb”? Of course you are not a bulb! In fact, besides its original meaning, the word can also refer to “the third wheel” in Chinese.
You might be wondering how come a 电灯泡 is related to the third wheel. Despite the fact that the slang word comes from Cantonese, a Chinese dialect widely used in Guodong, Shenzhen etc, we can understand its meaning in a much easier way: Imagine a couple of loved ones going on a date, they certainly want a quiet, dark, intimate setting where there is no “light bulb” over head. The bulb is just too bright for the couple to maintain their romantic atmosphere.
In Chinese, the term used for this situation is “当电灯泡”, which can be translated as “to be a light bulb”. 当 (dāng) has the meaning of “to be/to become”. The common sayings are:
bié dānɡ diàndēngpào!
别 当 电灯泡 !
Don’t be the third wheel!
wǒ bùxiǎng dāng diàndēngpào!
我 不想 当 电灯泡!
I don’t want to be the third wheel!
lì lì, jīntiān wǎnshɑng hé wǒmen yìqǐ qù kàndiànyǐng bɑ！
A: 丽丽，今天 晚上 和 我们 一起 去 看电影 吧！
Lily, come and watch movies with us!
suànle, wǒ zuì tǎoyà dāng diàndēngpào le！
B: 算了，我 最 讨厌 当 电灯泡了！
Forget it. I hate most to be the third wheel!