English for Writing Research Papers

6.11   Use of respectively to disambiguate
Respectively
 is a very useful word for clarifying how items are related to each other. 
In S1, a basic knowledge of geography makes it clear that London is associated 
with England, and Paris with France.
 
S1.  London and Paris are the capitals of England and France.
But such connections are not always so obvious, as in S2:
 
S2.  *… where X is the function for Y, and f1 and f2 are the constant functions for P and Q.
Are f1 and f2 constant functions for both P and Q? If so:
 
S3.  … and f1 and f2 are the constant functions for both P and Q.
Or is f1 for P and f2 for Q? If so, use respectively:
 
S4.  … and f1 and f2 are the constant functions for P and Q, respectively.
Most style books recommend placing respectively at the end of the phrase. It is best 
to put a comma before respectively.

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6.13 both … and, either … or