to keep one's attention on something

think about closely

the act, state, of deluding or being deluded; a false opinion or belief, especially one that may be a symptom of madness

misconception, misbelief

to think out, invent (a plan etc)

conceive, dream up

something which one seems to see or experience during sleep

illusion, vision

to make up (something false)

manufacture

wild or extravagant creative thought or mental pictures

imagination, dream

(an instance of) seeming to see something not actually present

dream, delusion

(the seeing of) something that does not really exist; a false or impossible idea

false appearance; false belief

a plan, idea etc that cannot happen or be successful

think about deeply and theorize

(an instance, occasion, of) a condition of being lost in dreamy, pleasant thoughts

daydream

to think, consider, form opinions (without having complete knowledge); to buy and sell goods, shares etc with the hope of profit from changes in their market value

think about deeply and theorize