To Pass Away, To Become Deceased, To Die
intransitive verb, godan verb
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb. This word is actually two words put together, though. 亡く means "be deceased." なる means "to become." So put that all together and you have to pass away or to become deceased. It's basically a polite way to say something died (死ぬ).
なくなる
To learn to read this kanji you have to remember the な part of 亡く, though our mnemonic will use the whole thing. If you're about to become deceased, you are probably knocking (なく) on death's door.
去年、母が亡くなった。
Last year, my mother died.
これは、亡くなった友人のための花です。
This is a flower for my friend who has passed away.
姉は、亡くなる前に「宝くじ...」と言いました。
My sister said "the lottery..." before her death.