Seniority can be used as a noun or an adjective.
Singular: Seniority | Plural: Seniorities
Thomas: How dare he even consider the idea the chair placements that I so carefully determined could be wrong! Justin, just because you are older than Simon does not mean you have seniority!
Justin: But sir! You know very well that I am by far the most dedicated member of this fine ensemble, and I have been a member for the longest! I practiced for hours to prepare for my audition!
Thomas: I have a prestigious degree in music education from Northwestern! You shouldn't challenge the superhuman hearing abilities of what God gave me. Anyone who thinks they deserve a higher placement because of seniority - well, I hope the door doesn't hit your rear end on the way out!
Jeff: But Thomas, with such a solid audition system, Justin should logically be the section leader, just like I am! Right Brett?
Brett: Absolutely, Jeff! With you as section leader, the logically determined Eagan High School Wind Ensemble Percussion Section is destined for greatness, especially with my highly productive lessons! Unfortunately, because I don't have any seniority, I won't be around next year to see it.
Real Simon: That's a shame, because he was such an experienced instructor - and good looking, too!
Sophmores and Juniors are usually accustomed to this power, however some freshman like to put up a stink about it.
*taps freshman in front of him*
Cool Freshman- whats up bro?
Senior- We are gonna play a game called Seniority!
C. Freshman- Damnit I always loose that game! How did you get so good
Senior- hahaha sorry tho im really thirsty
Douch Freshman- I don't think so, thats not fair.
Senior- Suck it. *steps in front*
D.F*goes and whines*