Dream

From dictionary.com....

dream

  [dreem]  Show IPA

noun

1.

a succession of images, thoughts, or emotions passing through the mind during sleep.

2.

the sleeping state in which this occurs.

3.

an object seen in a dream.

4.

an involuntary vision occurring to a person when awake.

5.

a vision voluntarily indulged in while awake; daydream; reverie.

I had such a nice, pleasant dream of being with a dear friend last night...

until I woke up and realized it was only a dream...

Did you ever have a dream that was so good that you were sad to wake up from it?