Such 和 so 的用法都需要相當大的篇幅才能說明清楚。本文僅就這兩者同義的「如此，這麼；很，非常」(to this degree; very) 的意思來說明一般使用上常見的錯誤。就此意思而言，such 為限定詞，後接名詞片語，而 so 為副詞，後接形容詞或副詞片語。
不過，在此有需要先說明一下名詞片語的結構。完整的名詞片語主要是由三個元素所構成：不定冠詞 (a/an) + 形容詞 + 名詞，其中名詞一定會有，但名詞若為複數可數名詞或不可數名詞，那麼該名詞片語就不會有不定冠詞，而形容詞可能存在、也可能不存在，所以最精簡的名詞片語可能只有名詞一個元素而已。
現在就來看看一般在使用 such 或 so 時常見的錯誤。例如：
- It was such an interesting party. (這是一場很有趣的聚會) (正)
The party was so interesting. (這場聚會很有趣) (正)
It was so interesting party. (誤)
It was a so interesting party. (誤) - Jessica’s such a smart woman. (潔西卡真是個聰明的女人) (正)
Jessica’s so smart woman. (誤)
Jessica’s a so smart woman. (誤) - It was such a shock. (那是非常令人震驚的事) (正)
It was so shocking. (它使人大為震驚) (正)
It was such shocking. (誤) － shocking 為形容詞。 - They’re such snobs! (他們真是自負傲慢的勢利鬼！) (正)
They’re so snobs! (誤) － snobs 為複數可數名詞。 - Those are such cool earrings. Where did you get them? (那些耳環很酷。你在哪裡買的？) (正)
Those are so cool earrings. Where did you get them? (誤) - We’ve had such awful weather lately. (最近的天氣非常糟糕) (正)
We’ve had so awful weather lately. (誤) － weather 為不可數名詞。 - I’m so glad to see you. (我很高興見到你) (正)
I’m such glad to see you. (誤) － glad 為形容詞。 - Tom sat there ever so quietly. (湯姆靜靜地坐在那裡) (正)
Tom sat there ever such quietly. (誤) － quietly 為副詞。
然而，當名詞前面是用 much, many, little 或 few 來修飾時，該名詞片語的前面要用 so，不可使用 such。例如：
- So much food was wasted every day. (每天都有很多食物被浪費掉了) (正)
Such much food was wasted every day. (誤) - There were so few doctors in Taiwan fifty years ago. (五十年前台灣的醫生很少) (正)
There were such few doctors in Taiwan fifty years ago. (誤) - We’ve had such a lot of problems with the new computer. (我們新電腦的問題真多 / 我們的新電腦問題太多了) (正)
= We’ve had so many problems with the new computer. (正)
We’ve had such many problems with the new computer. (誤) - There were/was ever such a lot of people/money. (超多的人/錢) (正)
= There were/was ever so many/much people/money. (正)
There were/was ever such many/much people/money. (誤) - Thanks (ever) such a lot. (太感謝了) (正)
= Thanks so much. (正)
在上面的例句中，such 和 so 的前面有時會加上 ever，這個副詞係用來加強 such 和 so 的語氣。Ever such 的意思和用法跟 such 完全一樣，而 ever so 的意思和用法跟 so 亦無不同。這與 never 在口語中經常用 ever 來加強語氣而說成 never ever (從不，絕不) 的用法雷同。例如：
- Hilary’s ever such a nice girl. (希拉蕊真是個好女孩)
- It’s ever so cold. (天氣很冷)
- I never ever drink beer. (我從來不喝啤酒)