Is the structure ~たいだけ a separate grammar point? See example:
お父さんは出張で疲れているだろうから、ねたいだけねさせてあげよ。
I understand that it translates to “… let him sleep as much as he wants”. Is this usage explained somewhere on Bunpro? I could not find it.
Welcome back to the forums!
You raise an interesting question that actually gets to the heart of what だけ really means in Japanese.
It’s typically translated/glossed as ‘only’ or ‘just’, but the fundamental idea of だけ is that it’s indicating an extent.
For example, if you take this sentence from the writeup on だけ:
日本語を勉強するのは、月曜日だけです。
I study Japanese only on Mondays.
Basically, what it’s saying is ‘the extent of when I study Japanese is on Mondays’.
In these terms, the だけ of 寝たいだけ isn’t doing anything significantly different. 寝たいだけ寝る means ‘to sleep to the extent that one wants to sleep’, which would be equiavalent to ‘as much as one wants’.
So it’s less that ～たいだけ is functioning in a completely different way, and more that the ‘extent’ nuance of だけ shifts a bit depending on what’s around it.
I do agree that this isn’t really covered at the moment in the grammar writeup for だけ. It’s referenced in the N5 vocab entry for だけ (with definition #2 and sentences with phrases like 家を買えるだけのお金, which is a similar nuance) as well as the N2 grammar point だけは, but it probably warrants at least a mention in the main だけ writeup, if not its own entry.
We’re in the midst of discussions amongst the team regarding missing grammar points or things to be added/clarified in the writeups, so we’ll definitely take note of this and make sure to find a good place to work in an explanation and some examples of this particular usage of だけ.
Hope this helps clear things up a bit for now, and thanks for bringing it to our attention!
Please feel free to come back and ask anytime you encounter something that’s unclear.
2 Likes
@John-Bunpro your explanation makes a lot of sense, thank you for sharing.
However, in my head if I try to understand だけ as “to the extent of …” its meaning will sometimes overlap with ほど、ぐらい or まで. Maybe in some use cases, they are interchangeable but I guess in most of them they are not. I will need to depend on the amazing explanations from the Bunpro staff to clarify those differences 
Good to hear that Bunpro is still evolving, your work is much appreciated.
1 Like