The prefix An means not; absence of

Word	Meaning
Anecdote	A story or personal item not generally known; short account of an amusing or interesting event
Anemia	A condition in which there are not enough red blood cells
Anesthetic	Substance that removes sensation with or without loss of consciousness
Anodyne	Creating an absence of pain
Anomaly	Irregularity
Anomalous	Irregular
Anonymity	The state of being nameless
Anarchy	Lack of government
Analgesic	Causing insensitivity to pain