In the book I'm reading I keep seeing constructs where I would expect a verb but get the noun form + する. Here's an example:

The ogre laughed loudly and said "I will eat you first little boy".

Why is it 大笑いして rather than 大笑って?  

Here's another one:

I will protect you.

Now I'm assuming the お here is honorific (he's talking to a princess). Why is it 守りします and not 守ります?



2 Answers 2


The two examples have different reasons.

The prefix 大{おお} always attaches to a noun, e.g. see 大辞林

おお 【大】



  1. [...]

  2. 程度のはなはだしいことを表す。「—あわて」「—にぎわい」「—騒ぎ」

  3. [...]

In the second example お守りします you correctly identified that お is honorific. The only thing that's missing is the observation that the honorific お also only attaches to nouns, so お守ります wouldn't work. This construction お+[masu-stem]+する is very common and also lends itself to raising the level of politeness by replacing する with (the proper conjugation of) 致す{いたす}.



「大笑いする」に似た表現に「大いに(or 大きく)笑う」(not 大笑う)がありますが、後者は文字数が多い分「大いに」をあえて強調する印象になります。



As expression similar to 大笑いする one has 大いに (or 大きく) 笑う (not 大笑う), but the latter being rather wordy, it would seem to be overly emphasizing 大いに.

Also, 「お守りする」 comes from applying the keigo construction 「お~する」 to 「守る」. 守りします would be a mistake.

  • Thanks for the answer. Unfortunately I'm only a beginner and I'm finding it really difficult to understand in Japanese. Commented May 3, 2015 at 14:09

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