Quite nearly
A word meaning to work closely with someone is collaborate.
Scrutinise.
compacted
Metonymy is the process of replacing one word with another, closely related word. For example, in the sentence "The orders came from the White House", it can be assumed that the orders came from the President because of the close relationship between the two words.
followed closely /under observation
"Ancient" is another word for very old.
Another word for closely related could be: - Connected - Akin - Alike - Complementary - Correlated - Dependent - Enmeshed - Interchangeable - Interconnected - Interdependent - Interrelated - Intertwined - Interwoven - Like - Similar
There are several: examine, study, assay, investigate.
another word for very large
Naming something by using a word that is closely related.
An afternoon out is the hint word for another word for a very special afternoon. An afternoon date is another word for the same.
interrogate, cross-examine, or grill