sweet dream or sweet dreams?

是 sweet dreamS 才對的. 當然, 如果你說 have a sweet dream 的話, 人家都明白你的意思的, 但要留意的是, good night, sweet dreamS 是 native speakers 的表達方式. 你可以試試以下的英語字典s連結網:

http://www.onelook.com

打了 sweet dream 之後, 它出現的搜尋結果, 也自動轉為 sweet dreamS 的!
你再click入去 dictionary.com的連結, 便會見到外國人是說後者的了.

2006-11-18 16:55:20 補充：
其他參考補充:physicallymake a differencesleep tight, don't let the bed bugs bite

2006-11-18 16:58:13 補充：
more than

Physicaly-Sweet Dreams ( Cause u have more then 1 dream every night....)

Normally, people say: Goodnight, sweet dream /sleep tight!

If you use Sweet Dream, i don't suppose it'll make much of a differents.....

So, both works 4 me! ^^