Third wheel, 第三个车轮？

No.自行车、摩托车、马车、手推车一般都是两个车轮。再加一个车轮就多余了，没什么用。

汽车、卡车一般都是4个车轮。再加一个车轮就多余了，没什么用。

因此，third wheel, fifth wheel就是多余的，无用的。等同于我们中文经常说的“当电灯泡”，不该出现的场合。比如，My sister will go to Florida with  her fiancé for a vacation. They asked me to go with them. I believe their invitation is just for  politeness. I gave them an  excuse not to go as I do not  want to be a third wheel(fifth  wheel).我妹妹和她男朋友要去佛罗里达度假。他们邀请我去。我相信他们是出于礼节。我不想当电灯泡，找了个借口谢绝了。

2021年的情人节（Valentine’s Day）,yahoo刊登了如下报道：

Selena Gomez Spent Her  Valentine's Day Being the Best-Dressed Third Wheel

From ELLE

Selena Gomez, officially single and dating here and there, spent  her Valentine's Day being a third wheel to the best of company:  her good friends Anna Collins and Fox Atticus Martindale. Collins shared three photos of the Valentine's Day dinner she had with  her boyfriend Martindale and  Gomez. The three dressed up,  Gomez in a chic black dress, and enjoyed a homemade cake  topped with strawberry roses.

来自《世界时装之苑》

Selena Gomez法律上是单身，到处约会，当电灯泡和她最好的伙伴度过情人节。

一对情侣（love birds）在一起，多一个人，就是third or fifth wheel.

和wheel相关常用的其他用法：

1、 big wheel—大人物、重要人物

2、 at(behind) the wheel—负责、掌管

3、 spin one’s wheels—徒劳，做无用功

4、 wheel and deal-- (政界、生意)不停地讨价还价、讲条件、谈判、订协议，为所欲为

5、 wheel horse---（马车的）辕马，忠实的工作者

6、 wheel chair---轮椅

7、 oil the wheel---行贿; 送礼; 使事情顺利进行; 给轮子加油

8、 take the wheel---开车

While we are enjoy the song---Take the wheel, Mr. Tian Feng is taking the wheel to deliver lamb, chicken, beef,wine, liquor to customers.

在我们欣赏take the wheel 这首歌的时候，田丰先生正在开车给客户送羊肉、牛肉、鸡肉，歌涅红酒、曹怀仁酱香白酒、纽倍乐保品。Hope you enjoy the third  wheel,but do not be a third wheel, be  lovebirds.