Buddhist nun
Specifically a female Buddhist monastic; the male equivalent is 僧 (そう).
After losing her husband, she became a nun.
She became a Buddhist nun at a young age and trained at a temple.
Catholic nun; sister
Used for Christian nuns; context distinguishes from the Buddhist sense.
The nuns were offering prayers at the convent.
Derogatory and dated; usually written in katakana as アマ. Strongly offensive.
That bitch lied again, didn't she?
Amagasaki
Slang abbreviation of 尼崎 (Amagasaki), a city in Hyogo Prefecture. Often written in katakana.
There's a drinking party in Amagasaki this weekend.
Internet slang for the online retailer Amazon. Typically written in katakana.
I ordered that book on Amazon.
It's cheaper to buy that book on Amazon.
She lives at the temple as a nun.
海女 (also read あま) means a female pearl or shellfish diver, a completely different profession from 尼, a Buddhist or Catholic nun.
Used for people in formal or counting contexts; a Buddhist nun is counted as a person.
Standard kanji for the nun senses; also used in the slang abbreviation for Amagasaki.
Katakana spelling is usual for the derogatory 'bitch' sense and common for the slang Amagasaki and Amazon senses.
From Sanskrit amba (mother) via Chinese, originally a respectful term for a female ascetic. The derogatory sense likely developed as a pejorative extension, and the slang abbreviations are modern shortenings.