Adverb placement: Predominantly, mainly, mostly

The placement of adverbs—which modify verbs, adjectives, or other adverbs—can substantially change the meaning of a sentence. You’ve probably run across example sentences illustrating the importance of correctly placing the adverb “only”:

Only I drive red cars; no one else drives them.

I only drive red cars; I do not park them.

I drive only red cars; I do not drive green cars.

I drive red-only cars; I do not drive multicolored cars.

I drive red cars only; I do not drive red motorcycles.

Perhaps because “only” is so often used as an example in grammar books, many writers place it correctly. However, in the course of my scientific editing, I routinely encounter other misplaced adverbs;  the usual culprits are “predominantly,” “mainly,” and “mostly.” Let’s look at some examples:

Eukaryote-specific rRNA is predominantly located on the surface of the ribosome.

Here, “predominantly” incorrect modifies the verb “located,” when in fact it should modify the adverbial phrase “on the surface of the ribosome”:

Eukaryote-specific rRNA is located predominantly on the surface of the ribosome.

In my experience, most errors of this type involve incorrect placement of the adverb before the verb instead of after it, as in all the following examples (corrected sentences are italicized):

• Under neutral conditions, the O-acyl isopeptides were predominantly converted to the corresponding monomeric amyloid β peptides.

Under neutral conditions, the O-acyl isopeptides were converted predominantly to the corresponding monomeric amyloid β peptides.

• Cystathionine β-synthase catalyzes the formation of H₂S, which predominantly exists as SH^– at physiological pH.

Cystathionine β-synthase catalyzes the formation of H₂S, which exists predominantly as SH^– at physiological pH.

• Most other anthropogenic emissions, such as emissions related to fossil fuel combustion, mainly occur in urban areas.

Most other anthropogenic emissions, such as emissions related to fossil fuel combustion, occur mainly in urban areas.

• Humans are mainly exposed to PAHs by three routes: digestion, inhalation and dermal contact.

Humans are exposed to PAHs mainly by three routes: digestion, inhalation and dermal contact.

Humans are exposed to PAHs by three main routes: digestion, inhalation and dermal contact.

• The inhibitory activity of the plant extract was mostly due to coumarin.

The inhibitory activity of the plant extract was due mostly to coumarin.

• The evolution of H₂O at 85–100 °C was mostly due to vaporization, whereas H₂O evolution at 300–350 °C was mostly due to intramolecular H₂O elimination.

The evolution of H₂O at 85–100 °C was due mostly to vaporization, whereas H₂O evolution at 300–350 °C was due mostly to intramolecular H₂O elimination.

Admittedly, none of these sentences is likely to be misinterpreted; the alternative meaning implied by the misplaced adverb doesn’t make much sense, at least to a native speaker of English. However, these subtle errors may momentarily confuse non-native speakers—and may distract discerning readers into focusing on the quality of your prose rather than the quality of your research.

So spend a few minutes using your word processor’s search function to confirm that you have correctly placed these three adverbs in your papers.

References

Coghill, Anne M., and Lorrin R. Garson. The ACS Style Guide: Effective Communication of Scientific Information, 3rd ed. (Washington, DC: American Chemical Society, 2006), p. 45.

Cook, Claire Kehrwald, Line by Line: How to Improve Your Own Writing (Boston: Houghton Mifflin, 1985), pp. 22–29.

Einsohn, Amy, The Copyeditor’s Handbook (Berkeley: University of California Press, 2000), p. 360.

Garner, Bryan, Garner’s Modern American Usage, 3rd ed.  (Oxford: Oxford University Press, 2009), p. 592.

Stevens, Matthew, Subtleties of Scientific Style (Thornleigh, Australia: ScienceScape Editing, 2007), p. 47.