Editing Tip: 'Respectively' and 'Namely'

The words ‘respectively’ and ‘namely’ are very useful when providing specific information to the reader, but each is frequently misused. Here are some examples of how to use these terms correctly.

Jacqueline Chretien, PhD, ELS

Jacqueline Chretien, PhD, ELS

Team Manager, Editing

PhD, Molecular and Cell Biology
University of California at Berkeley

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The words 'respectively' and 'namely' are very useful when providing specific information to the reader, but each is frequently misused. Here are some examples of how to use these terms correctly:

Respectively

This term should always be used for parallel lists (i.e., two lists with the same number of items), where every item in the first list corresponds to the item with the same position in the second list:

  • “The OD600 values for bacterial growth in the 20°C, 25°C, 30°C, and 37°C groups were 0.5, 0.6, 0.9, and 0.7, respectively.”
    This statement could otherwise be written as “The OD600 values for bacterial growth were 0.5 in the 20°C group, 0.6 in the 25°C group, 0.9 in the 30°C group, and 0.7 in the 37°C group.”
  • NOT "The OD600 values for bacterial growth were 0.5, 0.6, 0.9, and 0.7, respectively.”
    This sentence does not include a second list that corresponds to the values listed and defines their differences.

If 'respectively' comes in the middle of a sentence, it should be both preceded and followed by a comma:

  • “The OD600 values for bacterial growth in the 20°C, 25°C, 30°C, and 37°C groups were 0.5, 0.6, 0.9, and 0.7, respectively, at 2 hours, but all cultures reached saturation at 8 hours.”

Finally, be sure not to confuse 'respectively' with 'respective,' which is an adjective meaning 'separate':

  • “At the end of the meeting, the faculty returned to their respective offices.”

Namely

This word is useful when presenting a list that highlights the major or most important aspects of something:

  • “There are many cell cycle regulators, namely cyclins, CDKs, CKIs, and checkpoint proteins.”
    That is, there are many cell cycle regulators, but these four groups are particularly important.
  • “This study has several limitations, namely the small sample size and retrospective study design.”
    The study may have other limitations, but these are the main ones.

'Namely' can also be used when redefining a term, as a substitute for “i.e.”:

  • "The natural velocity provides us with a preferred time-axis at each point, namely, the time-axis for which the matter proximate to the point is at rest."

We hope that this post will help you use these two terms correctly in your writing. If you have questions about these terms or others as you are writing, contact us at [email protected]. Best of luck!

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