Difference between くらい and くらいに

Question

...., これ以上ないくらいに大きく目を見開いて、...　
she opened her eyes as wide as possible ...

I don't understand what に is doing here. I've seen plenty of examples where くらい acts adverbially without needing に. So why is it there, and what happens if I omit it?

If it helps, my literal understanding is to parse it as "to the extent that there is nothing more than this she widley opened her eyes".

I read this answer for particle の but that doesn't seem to apply here since に cannot (as far as I know) attach to ない.

Aside: does 目を見開く have some cultural significance e.g. does it represent concentration for example? The subject is currently beating a dog with a broom. It says that she made a 一 shape with her lips (seems like something you'd do if you were concentrating) and then the above sentence. I would normally associate wide eyes with fear (I don't think she's scared), but that would be passive. This sentence is active.

Answer 1

Both ～くらい and ～くらいに can function adverbially, and I don't see a difference in meaning between:

これ以上ないくらいに大きく目を見開いて・・・

and

これ以上ないくらい大きく目を見開いて・・・

Similar examples:

• 子供のときに京都に引っ越しました。/ 子供のとき京都に引っ越しました。
• 子供のころによく遊んだ公園 / 子供のころよく遊んだ公園
• すぐに伺います。 / すぐ伺います。
• まっすぐに立ってください。 / まっすぐ立ってください。
• しっかりと持つ / しっかり持つ
• ぼんやりと眺める / ぼんやり眺める

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does 目を見開く have some cultural significance e.g. does it represent concentration for example?

目を見開く can indicate concentration, but here in your example I think it shows 緊張 (tenseness) and/or 興奮 (agitation/excitement?) It can also be used to describe one's surprise, anger, fear, admiration, seriousness, etc.

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(By the way, 目を[見張]{みは}る typically represents surprise and/or admiration.)

Answer 2

I think the meaning of your sentence don't change if you omit に. I guess に is used to definition an adverbial function or just the emphasis.

I don't feel 目を見開く has some cultural significances. When man angry or when man are joyful, of course when man feel fear, in various situations, they open their eyes wide.

Answer 3

I suppose they are same, because they can be replaced. For example:

• 同じくらい(に)
• 小指くらい(に)

But くらいに is not very used. So I recommend to say くらい.

Answer 4

Japanese dictionary "goo" shows the meaning of "位（くらい）" as 3 patterns.

http://dictionary.goo.ne.jp/jn/63287/meaning/m0u/

I show you the usage of "に" for those model sentences. (explanations are ommited. See the original web site of the dictionary.)

１ 「一〇歳位の男の子」「その位で十分だ」

NG: 「一〇歳位に男の子」「その位に十分だ」

OK: 「今はもう、１０歳くらいに（は）なるだろう」、「いい加減にしろ。その位にしておけ」

OK: 「10歳くらいにはなる男の子」、「その位にはしても構わないだろう」

２ 「声も出ない位びっくりした」「犬位人間に忠実な動物はいない」「目に見えない位小さい」

OK: 「声も出ない位にびっくりした」「目に見えない位に小さい」

NG: 「犬位に人間に忠実な動物はいない」

OK:　「犬程に人間に忠実な動物はいない」＝「犬が示す程度に、人間に忠実な動物はいない」

３ 「簡単に否決される位なら、提案しなければよかった」

NG: 「簡単に否決される位になら、提案しなければよかった」

About the dictionary meaning 1st and 2nd, I can say that "位に" indicates the maximum value or degree that could be acceptable or realizable.