* Closeness: This refers to the state of being close, often in a physical or emotional sense. Example: "The closeness of their friendship was evident."
* Proximity: This refers to the state of being near or close in distance. Example: "The proximity of the airport made it noisy."
* Intimacy: This refers to a state of close personal connection, often romantic or emotional. Example: "They shared an intimacy that few couples achieve."
* Nearness: This is a more general term for being close in distance or time. Example: "The nearness of the exam made her anxious."
The best abstract noun to use will depend on the specific meaning you want to convey.