is a grammar point that utilizes the kanji 殊（こと）, meaning 'particularly' (in terms of a large amount). As these structures regularly appear in hiragana, they are not to be confused with 事（こと） 'thing'. こと is a combination of 'particularly', and the case marking particle
か, presenting a question.
In sentences with ことか
, words that highlight some particular number or extent are often used, before ことか
comes at the end of the statement, expressing that 'extent' as being particularly unusual, or even unbelievable (thanks to the addition of か). This is often translated simply as 'how (A)', 'what (A)', or even 'god knows (A)'. Let's look at a few examples.
God knows how many times I have gone to that person's concert.
How can I explain how cute my dog is? There is no other dog as cute as her.
God knows how bored I am. It's been a long time since I've been this bored.
God knows how worried I am to let my kid on the train by himself.
can be translated as 'to what particular (A) is (B)!?', as the enquiry is often not directed at anyone specifically, but instead presents itself as a question simply to emphasize its magnitude.
In modern Japanese, this expression is used primarily in written language, and has a tendency to sound either poetic, or dramatic. Because of this, it may sound unnatural in daily speech, unless the speaker is purposely being dramatic.
God knows how much I loved you! Still, you betrayed me.
God knows how nice it feels to have a stranger thank you.