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Evidence-based Grammar: Comparisons

Amy Volpert

Last year when we presented our special manuscript tips series, we received requests from some readers for a follow up article exploring grammar usage in scientific articles and journals. So, here we present a companion grammar column focusing on some of the most common grammar and language errors encountered in manuscripts submitted to the journal.

Researchers love comparisons and analogies. Comparison is essential for data analysis and validation—you can compare your sample to a standard or you can compare different treatments under the same conditions. Comparisons are also used to highlight the overall significance of a study, that is to say how the findings differ from or extend upon current knowledge.

“Like” vs. “Such as”

While “like” has become a place-holder in everyday speech, to the annoyance of many, it turns out that the word is also often used inappropriately in print. “Like” should be used when discussing something similar to, but not the same as, the desired item or result.

  • Example: “The muscular/mesenchymal layer left behind also preserved its in vivo structure, with the mesenchymal cores of the villi sticking out like bristles on a brush and the crypt beds visible as tiny holes in between.”

In contrast, the phrase “such as” should be used when listing concrete possibilities; the phrase can commonly be replaced with “for example” in the text or “e.g.” in parenthesis.

  • Example: “Organisms that are tolerant of extreme environmental stress, such as desiccation, accumulate large amounts of disaccharides in the dehydrated state.”

“Compared to” vs. “Compared with”

This is a more subtle distinction than in the case of “like” and “such as” above.

“Compared to” is correct when comparing items that are different or stating the similarities between items.

  • Example: “Target titrations indicated some differences in plate-based sandwich assay performance compared to the bead-based test.”
    *Since the two types of assays are different, “compared to” is appropriate here.

“Compared with” should ideally be used when comparing similar items or stating the similarities and differences between items.

  • Example: “The target sequence has GC content of 42.9%, compared with the mammoth mitogenome average of roughly 38%.”
    *Since two similar items (DNA sequences) are being analyzed, “compared with” is appropriate here.

Note: It is good to know this distinction between "compared to” and “compared with”, but in general practice, you can often get away with using the phrase you prefer.

“-er” vs. “-est”

In English, the suffix “-er” is used to compare one value relative to another (e.g., bigger, smaller). The suffix “-est”, however, is used to identify an extreme value (or subset of values) in a data set containing three or more elements (e.g., biggest, smallest).

The easiest way to think of this is that “-er” should be used when comparing two values relative to one another.

  • Example: “We show that this protocol can generate observable changes in the amount of cartilage tissue formed in micromass, unlike lower efficiency, higher cytotoxicity techniques.”

On the other hand, “-est” should be used when identifying data points at either end of a range of values (assuming the data set has more than three items): “The expression of gene X was greatest in adult subjects compared to neonates or juveniles.”

  • Example: “The algorithm should attempt to identify the deepest taxonomic rank possible.”

“Greater than” (>) vs. “Greater than or equal to” (≥) [or “Less than” (<) vs. “Less than or equal to” (≤)]

Everyone should know the difference between the phrases “greater than” (>) and “greater than or equal to” (≥), but when it comes to discussing data, it is important to double-check that you are using the right term (or symbol). It’s very easy to slip and say that a set of values is greater than 50, when the truth is that the set contains values of 50 or greater.

  • Example: “A major limitation in miRNA library construction arises when the amount of input RNA <200 ng.”
    *This limitation would not been seen with 200 ng of input RNA.
  • Example: “Sites with a maximum of 2 alleles and a minor allele frequency ≥2% were selected.”
    *A site with 0–2 alleles and a minor allele frequency equal to 2.0% could be selected.

We hope these examples start you thinking more about the way in which you word comparisons in your manuscripts. A simple turn of the phrase can have a profound impact on the way a reader or reviewer perceives your text.