(n.) Action of the brain, whether conscious or unconscious.

abstract thought act of thought application boning cerebration cogitation conceit conception conceptualization conning contemplation cram cramming creative thought deliberation drill engrossment excogitation exercise extensive study grind grinding headwork heavy thinking idea ideation imageless thought inspection intellection intellectual exercise intellectualization lucubration mental act mental labor mental process mentation noesis perusal practice ratiocination reading reasoning reflection restudy restudying review speculation straight thinking study studying subject swotting thinking thinking aloud thinking out thought wide reading