Here are a few possibilities:
* Appointment: This is the most direct and common abstract noun. It refers to the act of being appointed.
* Designation: This emphasizes the formal assignment of a role or position.
* Assignment: This focuses on the task or duty given to someone.
* Selection: This highlights the choice of a specific individual for a position.
The best abstract noun to use will depend on the specific meaning you want to convey.
For example:
* "He received his appointment as ambassador." (Focus on the act of being appointed)
* "Her designation as project manager was well-deserved." (Focus on the formal title given)
* "The assignment was challenging but rewarding." (Focus on the task given)
* "The selection committee chose the best candidate." (Focus on the choice made)