* Seniority: This is the most common and general abstract noun for "senior," referring to the state of being senior or having more experience.
* Eldership: This specifically refers to the state of being an elder, often associated with wisdom and authority.
* Preeminence: This implies a position of superiority or leadership due to seniority.
* Precedence: This refers to the right to be heard or considered first, often due to seniority.
The best abstract noun to use will depend on the specific situation and the meaning you want to convey.