As defined by Urban Dictionary, a Third Wheel is "one who deters the socialization of a couple, perhaps when being invited out of pity or through a feeling of duty. This person may be eased into the situation by being allowed to stay in an environment he or she has become accustomed to (perhaps a kitchen, where the third wheel can bake cookies for the couple.) The third wheel may feel uncomfortable about watching the couple canoodle on his her her sofa, but none of this is taken into consideration."

Pretty much - they are always the odd one out and no one really cares. The Third Wheel is a position applicable to all sorts of relationships- romantic, friendly, work, etc.

I am a 21-year-old seasoned veteran at the Third Wheel position. Sometimes I pride myself in it, but most times, it frustrates me that no one really cares and they just think it's funny and that I actually enjoy being a third wheel. Because I don't. Literally no one does. There's a lot that us third wheels don't tell the other two wheels, so here goes.

To the girls:

Don't get me wrong, I love hanging out with you. You're significant other is pretty cool too. Thank you for including me, and allowing me to be a part of your relationship, but have mercy, stop acting like I'm a charity case. I don't need that. I am fully capable of a social life outside of your relationship, so please do not flatter yourself that much.

Stop bringing up inside jokes between you and your boo when we're all hanging out. It just further emphasizes that I am the odd one out and that I could never be a full part of the group. Not cool.

Also, I'm not kidding on this one either, don't you ever, ever, ever, ever, call me the third wheel when the three of us are hanging out. I know full well what my position is and what it means- it means that I am alone. I do not need you labeling me as well.

To the guys:

Alright buddy. So you've made it far enough that she doesn't mind all of us hanging out. So that means she actually likes you. It also means that I get to share my honest opinion of you at any time I want. Be careful.

If you open a door for her, it better stay open for me. I am a lady that deserves just as much respect as she does. If it shuts in my face, there's a good chance I won't be seeing your face around for much longer.

No, I am not interested in your other single friend. If we all plan to hang out and you bring your single friend I've never met before, you (and maybe him as well, depends on my judgement) will be promptly asked to leave. I don't play those games.

To all:

I'm not trying to hate on anyone. Don't mistake me being annoyed, with me being jealous. When I am jealous, it's not that I'm jealous that y'all are in a relationship, I just know that I can be easily replaced, and watching it happen right in front of me isn't fun.

All in all, I'm honored that all of the wheels, you chose me to complete your tricycle.

"Man, I know how you feel—third wheel. I have been the third wheel so many times in my life…my mom told me something once that made me feel a lot better. She said the third wheel is what makes it a tricycle." - Michael Scott