What's the purpose of "し" after "買い物" in this sentence?


昨夜スーパーへ買い物しに行きました。

I understand the purpose of the "ni" particle, but why does it need the "shi"?
Did I miss something?

Thanks.




> What's the purpose of “し” after “買い物” in this sentence?  
>  昨夜スーパーへ買い物しに行きました。
>
> I understand the purpose of the "ni" particle, but why does it need the
> "shi"? Did I miss something?

It doesn't need, and must be colloquial, but not wrong. We say 買い物をしに行く,
買い物しに行く, or 買い物に行く. This し is just the conjugated version (連用形) of する. And に
is a particle to show a purpose of the action expressed by the following verb.

  * 食事しに行きませんか？ ＝食事に行きませんか？
  * 宿題しに友だちがもうすぐ来る。(I find this one is not very natural without this し.)

