Everyday 和 every day 有分別嗎？

今天在某牌子曲奇餅的罐上發現了一句錯的英文句子： 

Our cookies are baked fresh everyday.     

錯誤在於 everyday 這個字。正確的寫法應該是： 

Our cookies are baked fresh every day. 

它們的分別在於 "everyday" 是一個形容詞 (adjective)，它後面需要接一個名詞 (noun)，譬如說 everyday life 和 everyday use： 

Mobile phones have become part of everyday life.
I need a good computer for everyday use.  
Helping the needy is his everyday activity. 

跟 "everyday" 不同，"every day" 是一個 adverb phrase； 它的作用是為句子中的 verb 帶來更多資料： 

I play the piano every day. 
My cat eats a packet of dried fish every day. 
He helps the needy every day.   

留意以下的對比： 

These plates are for everyday use.
We use these plates every day.

Gossiping is part of everyday life in Hong Kong.
People in Hong Kong gossip every day.