In the ももたろう tale there's a sentence that goes like:

> おじいさんが山{やま}へ木{き}を切{き}りにいけば、  
>  おばあさんは川{かわ}へせんたくにでかけます。

Which translates as

> If the old man went to the mountain to cut trees  
>  the old woman would go out to the river to wash clothes.

In the old woman's case the verb せんたく is presented in its dictionary form and
is not modified by the particle に, which gives the sense of purpose (to go out
_to_ do something). So why the same is not true for the old man? Why 木を切りに
instead of 木を切るに?
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2016-01-17T21:37:07.937
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2016-01-20T05:54:24.233
2016-01-20T05:39:44.663
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question
particles verbs conjugations nouns
木 を 切り に VS 木 を 切る に in the ももたろう tale
[verb in masu-form + に行く] essentially means go to {place} to do {verb}

So, in this case :

おじいさんは山に行く。

The old man is going to the mountain

何故山に行くのか？

Why is he going to the mountain?

木を切りに行く。

He's going to chop wood

Does that make things a little clearer?
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2016-01-19T18:13:26.677
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answer
In your case, you are asking about a specific construct: the use of

> purposeに+verb of movement

To express:

> Going somewhere to do something

This pattern can take two kinds of objects as purpose:

  * The ~ます stem of a verb: "Going somewhere to _verb_ '. Note that is similar to _nominalizing_ the verb, see for example [this question](https://japanese.stackexchange.com/questions/12970/%E5%A7%8B%E3%81%BE%E3%82%8B-%E5%A7%8B%E3%81%BE%E3%82%8A-is-there-a-rule-of-making-nouns-from-verbs-besides-nominalization).
  * A noun: "Going somewhere to do _noun_ "

In your case:

  * 洗濯{せんたく} is a noun, we can directly place it in front of に, hence 川へ洗濯に行く. Quite literally, "going to the river to _do_ the laundry".
  * 木｛き｝を切｛き｝る is a verb. Thus, we turn it into its ~ます stem, leading to 木を切りに行く. This time, meaning "going to the river to _cut_ some wood".

Note that if you absolutely want to use a verb, you can use 洗濯する, which
becomes:

> おばあさんは川へ洗濯 **し** にでかけます

This is much more infrequent, and I would advise against using it in general,
unless the sentence is ambiguous without する.
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2016-01-20T05:35:28.087
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answer