impression

/im-ˈpre-shən/

noun

  1. the effect produced by impressing: such as

  2. an especially marked and often favorable influence or effect on feeling, sense, or mind

  3. a stamp, form, or figure resulting from physical contact

idea concept conception thought notion impression mean what exists in the mind as a representation (as of something comprehended) or as a formulation (as of a plan). idea may apply to a mental image or formulation of something seen or known or imagined, to a pure abstraction, or to something assumed or vaguely sensed. concept may apply to the idea formed by consideration of instances of a species or genus or, more broadly, to any idea of what a thing ought to be.

idiom

  1. to have an idea or belief that is usually not clear or certain

I was under the impression that admission was free.