亡くなる

Etymology
The adverbial -く (-ku) form of adjective + verb : literally, "to become not, to become nonexistent".

The spelling of the na- root of nai and naku naru is reserved for the meaning of "dead, gone".

Cognate with.

Verb

 * 1)  to die

Synonyms

 * See Thesaurus:死ぬ