The word "respectively" is frequently misused by native and non-native English-speaking authors alike, and, as with the other elements described above, its misuse can lead to confusion and ambiguities. It is often clearer not to use this term at all, but it can be useful to economize on words where there are two corresponding lists.
Respectively is quite useful in the sentence “The latencies to withdrawal from a painful stimulus in control and transgenic mice were 3 s and 2 s, respectively,” meaning that control mice withdrew after 3 s and transgenic mice withdrew after 2 s.
When describing something much shorter than “The latencies to withdrawal from a painful stimulus,” such as average weights, respectively is not necessary. “Control mice weighed 20±3 g and transgenic mice weighed 17±2 g” is better than “Control mice and transgenic mice weighed 20±3 g and 17±2 g, respectively,” which contains one additional word.
Note that “respectively” can only be used to refer to two corresponding lists at one time, and cannot be used to refer to more. Thus the sentence “The latencies to withdrawal from 5 g and 10 g painful stimuli in control and transgenic mice were 3 s and 2 s, respectively” is incorrect and impossible to understand.
- “The proportions of monocytes positive for CD163, CD7 and CD11a were 45%, 63% and 70%, respectively.” In this sentence, the “respectively” makes clear that the three percentages refer to each of the three markers in the same order.