third wheel or fifth wheel

fifth wheel or third wheel

Meaning:
a person who is in a situation where they are not needed; an extra and unnecessary person or thing; also know as “fifth wheel”

Examples:

1. I was the only person at the dinner party without a date. I felt like a third wheel.
2. I felt like a fifth wheel when i couldn't speak English well with my English teacher.
3. I'm going, I don't want to be a fifth wheel.
4. I quit my bank job and am preparing for civil service. Now I feel like I am a third wheel.
5. The way I live my life, I always feel like a fifth wheel.

Origin:

This phrase originated from extra wheel that was on four wheel coaches, carriages and wagons (American).