Correlative conjunctions come in pairs. One pair of these
conjunctions works together to relate two items of equal rank. The common
correlative conjunctions are:
Both--and
Either--or
Neither--nor
Not--but
Not only-- but also
Whether--or
Look at the following sentence:
Not only the human caretaker
but also the monkey was rescued from the collapsed monkey
exhibit.
Here, the correlative conjunction "not only--but
also" relates the human caretaker and the monkey--two grammatically equal
words.