How to write and publish a scientific paper - Barbara Gastel, Robert A. Day 2022

Special problems
How and when to use abbreviations
Scientific style

A frequent problem with abbreviations concerns the use of a or an with them. Should you write “a M.S. degree” or “an M.S. degree”? Recall the old rule that you use a with words beginning with a consonant sound and an with words beginning with a vowel sound (for example, the letter “em”). Because in science we should use only common abbreviations, those not needing to be spelled out in the reader’s mind, the proper choice of article should relate to the sound of the first letter of the abbreviation, not the sound of the first letter of the spelled-out term. Thus, although it is correct to write “a master of science degree,” it is incorrect to write “a M.S. degree.” Because the reader reads “M.S.” as “em ess,” the proper construction is “an M.S. degree.”

In biology, it is customary to abbreviate generic names of organisms after first use. At first use, you would spell out “Streptomyces griseus.” In later usage, you can abbreviate the genus name but not the specific epithet: S. griseus. Suppose, however, that you are writing a paper that concerns species of both Streptomyces and Staphylococcus. You would then spell out the genus names repeatedly. Otherwise, readers might be confused as to whether a particular “S.” abbreviation referred to one genus or the other.