Institution
Part of speech: noun
Definition: An established organisation, especially one dedicated to education, public service, culture or the care of the destitute, poor etc. The building which houses such an organisation. A custom or practice of a society or community - marriage for example. A person long established with a certain place or position. The act of instituting.
Example sentence: A founder can carry an institution only so far, and then others have to step in, even the alumni. That's how an institution becomes one.
Establishment
Part of speech: noun
Definition: The act of establishing; a ratifying or ordaining; settlement; confirmation.The state of being established, founded, etc.; fixed state.That which is established; as a form of government, a permanent organization, business or force, or the place where one is permanently fixed for residence.The establishment: the ruling class or authority group in a society; especially, an entrenched authority dedicated to preserving the status quo.
Example sentence: I sincerely believe... that banking establishments are more dangerous than standing armies.