Daydreaming

noun a state of being forgetful or inattentive

adjective absentminded

• Her absentmindedness often caused her to forget important meetings.
• I can't believe I left my keys at home again, my absentmindedness is getting out of hand.
• His absentmindedness is next level, he's always losing his phone.
• The absentmindedness of the professor led to a confusing lecture for the students.

noun a large building or group of buildings fortified against attack with thick walls, battlements, towers, and in many cases a moat

preposition a word governing, and usually preceding, a noun or pronoun and expressing a relation to another word or element in the clause

• The idea of starting a business without a solid plan is like building a castle in the air.
• Thinking about becoming a millionaire overnight is just like building a castle in the air.
• Dreaming about winning the lottery is like building a castle in the air.
• His plans for a lavish vacation seemed like a castle in the air, considering his limited budget.