Amnesia (noun)

Partial or complete loss of memory, especially as a result of injury, shock, or illness.

Origin:

Late 19th century: from greek amnēsia, from a- "without" + mnēsikos "of memory".

Examples:

1. She suffered from amnesia and couldn't remember her past.
2. The accident caused him to have temporary amnesia.
3. The amnesia was caused by a blow to the head.
4. The patient's amnesia was caused by the stroke.
5. The amnesia was caused by a traumatic event in the past.