Daydreamer (noun)

1. A person who indulges in idle fantasies, especially while awake.
2. A person who is often lost in thought and not paying attention to their surroundings.

Origin:

Early 19th century: from daydream (verb), on the pattern of daydream.

Examples:

1. He was a daydreamer, always lost in his thoughts.
2. She was a daydreamer, always thinking about her future.
3. The daydreamer is often lost in their own thoughts.
4. The daydreamer is not paying attention to the present moment.
5. The daydreamer is someone who indulges in idle fantasies.