so和so that

(1)文法學者R. Quirk舉過一組例句：

We paid him immediately, so (that) he left contented.

我們立刻付錢給他，故他滿意地離開了。
We paid him immediately, so (that) he would leave contented.

我們立刻付錢給他，好讓他滿意地離開。
可見在非正式語體中，so和so that有時可互換。
(2)在非正式語體中，so…that中的that或可省略，例如：

Her parents gave her so many toys (that) she couldn't possibly play with them all.

她父母給她那麼多玩具，令她玩都玩不過來。

又見陸谷孫《英漢大詞典》：

At night it was so cold (that) I couldn't sleep at all.

夜裏冷得我完全睡不。
換一種說法，即so和so…that有時可互換。
(3)此種句子省略that，有時也可加逗號分開句子兩部分，意思沒多大分別，例如：

It was so cold that I could hardly keep still.

It was so cold, I could hardly keep still.
那時太冷，我無法保持不動。