Absence is simply defined as "Not being there."
Absence typically refers to the state of being away or not present. It can also describe a lack or deficiency of something, such as absence of mind (distraction) or absence of evidence.
Aplasia is the medical term meaning absence of development.
Asplenia is the medical term meaning absence of the spleen.
Athelia means absence of a nipple.
presence
Aphakia is the medical term meaning absence of the lens. This is often a result of cataract surgery.
Athelia is the medical term meaning absence of nipples.
Anhidrosis is the medical term describing the absence of sweating.
arrhythmia
The medical term for absence of the external ear is "anotia." This condition involves complete absence of the external ear.
Anencephaly.
According to internetslang.com, it means "leave of absence". :)
anhydrous