When you wish someone a pleasant night of sleep, you can say "sweet dreams" or "sleep tight".
"Sweet dreams"= I hope you have pleasant dreams
"Sleep tight"= I hope you sleep well/I hope you sleep soundly.
There are many ways to say goodnight to one and express that you would like them to have a good nights sleep or sweet dreams. You may make use of any of the following expressions;
''Have sweet dreams.'' A common way of saying goodnight in English, expressing that you would like the other person to sleep peacefully. You may also say ;
''Sleep tight, don't let the bedbugs bite.'' It generally has the same meaning and is a common English expression derived from a bedtime rhyme.
人に[おやすみ](https://eikaiwa.dmm.com/uknow/questions/36353/)を言い、ぐっすり眠れるように伝える表現はたくさんあります。以下のように言うことができます。
''Have sweet dreams.''
いい[夢](https://eikaiwa.dmm.com/uknow/questions/52182/)を見てね。
英語でおやすみを言い、すやすや眠って欲しいことを伝える一般的な表現です。
''Sleep tight, don't let the bedbugs bite.''
おやすみ。ぐっすり眠ってね。
これも同じ意味で、ベッドタイムのライム（韻）からきた英語の一般的な表現です。
"Sweet dreams" is the most common way to wish some a good night's sleep and that they have good dreams in their sleep. "Pleasant dreams" is also very common, but less intimate. Usually "sweet dreams" is used for family members, children, parents, lovers and close relationships, as well as "pleasant dreams", but you can also say "pleasant dreams" to a person whom you do not have a really close relationship or simply say "have a good night's sleep" for more formal relationships.
"Sweet dreams"は、ぐっすり眠って、いい夢を見て欲しいことを願う最も一般的な表現です。"Pleasant dreams"もとても一般的ですが、よりフォーマルです。
"Sweet dreams"は大抵、家族、子供、両親、愛する人、近い関係の人に使います。"Pleasant dreams"も同様にそのような人たちに使うことができますが、それほど近くない人にも使えます。もしくは、よりフォーマルな関係の人には、"have a good night's sleep" （ぐっすり眠ってください）と言えます。
If you want to wish someone to have good dreams you can say:
I hope you have good dreams.
I hope you have good dreams tonight.
I hope you have the best dream tonight.
I hope you have pleasant dreams tonight.
Sweet dreams.
You can also wish someone a good nights rest by saying:
I hope you sleep well.
I hope you have some good rest tonight.
Take care and rest up.
Parents sometimes say this to their children. A funny way people tell someone to sleep well is:
Good night, sleep tight and don't let the bed bugs bite.
相手にいい夢を見て欲しい気持ちを伝えるなら、次のように言えます：
I hope you have good dreams.
（いい夢が見られるといいですね）
I hope you have good dreams tonight.
（今晩はいい夢が見られるといいですね）
I hope you have the best dream tonight.
（今晩は最高の夢が見られるといいですね）
I hope you have pleasant dreams tonight.
（今晩は素敵な夢が見られるといいですね）
Sweet dreams.
（いい夢を）
また、以下のように、ぐっすり眠って欲しい気持ちを表すこともできます：
I hope you sleep well.
（ぐっすり眠れるといいですね）
I hope you have some good rest tonight.
（今晩はぐっすり休めるといいですね）
Take care and rest up.
（ぐっすり休んでください）
親は子供にこんな風に言うこともあります。ぐっすり眠って欲しいことを伝える面白い表現です：
Good night, sleep tight and don't let the bed bugs bite.
（おやすみ。ぐっすり眠ってね）
The two sentences you see above are great ways to tell someone goodnight. Both of these sentences are common terms in our everyday conversation in English, so they would make great additions to your vocabulary. These sentences would be appropriate when talking with close friends or family. I hope these two sentences and this explanation help you out!
When you want to tell someone to sleep well and have a nice dream, you can use the phrase "sweet dreams".
For example, you can say:
-Goodnight and sweet dreams.
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アメリカ合衆国 
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