reverie
A pleasant daydream where your mind happily wanders.
A reverie is a pleasant daydream where your mind drifts away from what's happening around you into your own thoughts and imagination. When you stare out the classroom window and suddenly you're thinking about building a treehouse or replaying your favorite scene from a book, you're lost in reverie.
Unlike focused daydreaming where you're planning something specific, reverie feels more like floating. Your thoughts wander freely from one pleasant idea to another. Maybe you're remembering last summer's vacation, then imagining next weekend's sleepover, then thinking about what it would be like to live in ancient Rome. One thought leads gently to another without any particular goal.
The word carries a peaceful, almost magical quality. When someone is in a reverie, they often have a distant, dreamy look on their face. A character in a story might be interrupted from her reverie when a friend calls her name three times before she finally hears it.
Reverie is different from spacing out because it feels good, like taking a mental vacation. It's your imagination running free in a way that's relaxing and enjoyable rather than worrying or planning.