なのである LinksSentence search for なのであるEdit in JMdict Auxiliary verb, Godan verb with 'ru' ending (irregular verb)1. it is assuredly (that) ...; can say with confidence that it is ...See also なのだいくつになってもこども子供はこども子供なのである。No matter the age, a child is a child. Discussions Log in to talk about this word.