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Editing Tip: When to Use "And" and "Or"

  • The conjunctions ‘and and ‘or’ have very different meanings, yet they are still confused at times
  • Take care when describing your results; using ‘and’ in place of ‘or’ could cause the reader to misunderstand your observations
  • Consider adding ‘both’ or ‘either’ for clarity

The conjunctions and and or connote very different meanings. In particular, and suggests the joint consideration of two concepts, whereas or suggests exclusivity. Consider the following two examples:

  • Enzymatic activity was not affected by changes in temperature and pH.
  • Enzymatic activity was not affected by changes in temperature or pH.

The use of and in the first sentence implies that enzymatic activity was not affected when temperature and pH were both changed. In other words, one experiment, in which two variables were altered, was performed. In contrast, the second sentence indicates that a temperature change did not influence enzymatic activity and that a separate pH change did not affect enzymatic activity either. In this case, two experiments were conducted, with one variable altered in each.

Additional words for clarity

To further emphasize that the two variables were manipulated together or separately, the terms both and either, respectively, could be implemented:

  • Enzymatic activity was not affected by changes in both temperature and pH.
  • Enzymatic activity was not affected by changes in either temperature or pH.

An additional option is as follows:

  • Enzymatic activity was not affected by changes in temperature and/or pH.

This phrasing combines the meaning of and and or, signifying that three experiments were performed, all with the same outcome of unchanged enzymatic activity: experiment 1, varied temperature; experiment 2, varied pH; and experiment 3, a combination of varied temperature and varied pH.

We hope that this post has elucidated the distinct implications of the terms and and or. Please contact us at [email protected] with any comments or questions. We wish you the best in research and writing!

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