The idiom "sweet dreams" is used to wish someone a good night's sleep and pleasant dreams. It is a way of expressing your hope that the person you are speaking to will have a peaceful and restful night's sleep.
You can use this idiom when saying goodbye to someone before they go to bed, or when you want to express your concern for their well-being. It is a friendly and caring way to wish someone a good night's sleep.
For example, if you are talking to your friend on the phone and they mention that they are feeling tired, you might say, "Okay, well I'll let you go get some rest now. Sweet dreams!"
In summary, "sweet dreams" is a way to express your hope that someone will have a good night's sleep and pleasant dreams.
• As I tucked my daughter into bed, I kissed her forehead and said "sweet dreams!".
• Before going to bed, I always tell my son "sweet dreams!".
• Sweet dreams! Don't forget to set your alarm for tomorrow morning.
• I had a great time with you tonight. Sweet dreams, and I'll see you tomorrow.
• After a long day of traveling, I collapsed into my hotel bed and muttered "sweet dreams" to myself before dozing off.
• The last thing I heard before drifting off to sleep was my partner whispering "sweet dreams!" in my ear.