「のは～だ」Give new and important information
「のは～だ」Give new and important information
Introducing new, significant information about something
The structure AのはBだ is used to introduce new, significant information about something, with B being the new information. B can be either a noun or noun phrase.
1
Basic usage with a noun or noun phrase in B.
この学校で一番かわいいのは彼女だ。
The cutest one in this school is her.
Special Note
Particles can also be used after the noun in B, with the exception of を and が.
このことを私に教えてくれたのは中村さんがだ。
The one who taught me this was Nakamura-san.
このことを私に教えてくれたのは中村さんだ。
The one who taught me this was Nakamura-san.
Other particles are fine to use after the noun or noun-phrase.
このことを聞いたのは中村さんからだ。
The one I heard about this from was Nakamura-san.
2
When used in the structure of AのはBからだ, it can be used to express a situation or event and then state the reason for it.
あなたの人生が駄目なのは、酒を飲むからだ。
(The reason) that your life is hopeless is because (you) drink alcohol.
Formation
食べるのは～だ・食べたのは～だ
安いのは～だ・安かったのは～だ
静かなのは～だ・静かだったのは～だ
学生なのは～だ・学生だったのは～だ
General Structure
一番かわいいのは、彼女だ。