事なの
(A) is (Description of A), (A) means that (Description of A)
Structure
Phrase + というのは(1) + Verb + （という）ことなの(2)だ(3)
Phrase + というのは(1) + ［な］Adjective + な(4)ことなの(2)だ(3)
Phrase + というのは(1) + Noun + の(4)ことなの(2)だ(3)
(1) って、とは、ということは、というのは
(2) なん
(3) である、でござる
(4) という
Explanation
When the noun こと (or its kanji form, 事) is used with なの, it functions to provide an explanation or definition, much like the んです・のです grammar structure. Similar to んです, using ことなの adds emphasis, changing a simple statement 'it is (A)' into 'the fact of the matter is that it is (A)'.
ことなの can appear in slightly different forms and is very commonly paired with というのは. In sentences like these, というのは introduces the term being defined, and ことなの follows with the speaker's explanation or definition of that term.
This grammar pattern can be attached to verbs and い-Adjectives in their plain form, な-Adjectives followed by な, and nouns followed by の.
- 先生というのは生徒に教える人のことなのだ。A teacher is a person who teaches students.
- 辞書というのは言葉の意味を調べる物の事なんだ。A dictionary is an object for looking up the meaning of words.
- 食事を取るというのは何かを食べることなのです。'To have a meal' means to eat something.
The word という can also appear immediately before ことなの. However, it is not always required and is less likely to be used if というのは has already appeared earlier in the sentence.
- パーティーに来られないということなの？So you're saying you can't come to the party?
- 読書とは本を読むことなの。'Reading' means to read books.
Caution
In casual conversation, the phrase というのは is often abbreviated to the shorter forms って or とは.
Caution
ことなの is also commonly used when forming questions. It is particularly useful when a speaker wants to confirm a conclusion they have reached based on what someone has said or done.
- つまり、もう宿題は終わったということなのか。In other words, does that mean you've already finished your homework?
- そんなに泣くことなのですか。Is it really something to cry so much about?
The form なのか is frequently encountered in fictional media such as anime, manga, and novels, but it can come across as blunt or rude in real-life conversations.
Examples
猫舌とは熱いものが食べられないという事なのだ。
'Nekojita' (cat tongue) means not being able to handle hot food.
空が赤いということは、台風が来るという事なのだろう。
A red sky means a typhoon is probably on its way.
「一期一会」とは、どういう事なのですか。
What exactly does 'ichi-go ichi-e' mean?
ポリグロットとは、たくさんの言語を話せる人の事なのである。
A 'polyglot' is a person who can speak many languages.
ドキドキするというのは、緊張しているという事なのだ。
Having a racing heart means that you're nervous.
彼がパーティーに来なかったのは、怒っているという事なのだろう。
The fact that he didn't come to the party probably means he's angry.
「サステナビリティ」とはどういう事なのだろうか。
I wonder what 'sustainability' really means.
学生であるということは、勉強しなければならないという事なのだ。
Being a student means you have to study.
信号が赤いのは、渡ってはいけないという事なのである。
A red traffic light means that you must not cross.
深々とお辞儀をするのは、深い敬意を示すという事なのだ。
Bowing deeply means showing great respect.
この冗談が分かるという事は、君のユーモアのセンスがかなり独特だという事なのだ。
The fact that you understand this joke means that your sense of humor is quite unique.
図書館とは、無料で本を借りられる場所の事なのである。
A library is a place where you can borrow books for free.