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  • Writer's pictureEmma Perez-Costas

Effect and Affect

I was quite surprised when I discovered how prevalent is the confusion between "effect" and "affect", at least for american students and "scientists in training". Thus, my first little morsel on editing and writing will simply define these two words.

EFFECT is defined in the mighty Merrian-Webster dictionary as:

1) "a change that results when something is done or happens : an event, condition, or state of affairs that is produced by a cause"

2) "to cause (something): to make (something) happen"

While AFFECT is generally defined as:

1) "the conscious subjective aspect of an emotion considered apart from bodily changes; also : a set of observable manifestations of a subjectively experienced emotion"

2) "to produce an effect upon: as

a : to produce a material influence upon or alteration in <paralysis affected his limbs>

b : to act upon (as a person or a person's mind or feelings) so as to produce a response : influence"

Here there is an example of their correct use in a scientific context:

  • When we block the expression of the mRNA encoding a specific protein, the final effect of this manipulation is that the protein will not be synthesized.

  • But, we affect the synthesis of the protein by blocking the expression of its mRNA.

Note that both sentences are providing almost the same information. But the effect is the result produced by blocking the expression of the mRNA, while affecting the expression of the mRNA is what produces the final effect.

Hope that this is helpful!

© Emma Perez-Costas, PhD. Science Editing Services. December 29th, 2014.


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