noun
absence
AB-suns/ˈæbsəns/
The state of being away or not present.
The empty chair and untouched cup make the other person's absence conspicuous.

Etymology
“Away” and “be” combine in the idea of being away. The abstract noun turns that condition into the state of not being present.
In context
food scraps and other organic material are broken down by bacteria in the absence of oxygen which produces methane
More examples
- The teacher recorded three absences this week.
- The absence of streetlights makes the road difficult to follow.
- He took charge during the manager's absence.
Forms
absence · absences
Similar words
- lack
- Means not having something rather than someone's being away.
- nonattendance
- Specifically means not being present at an expected event.