General Rules for Words
To make a noun plural in most cases you just add “s” such as patients or ideas. For words ending in s, x, ch, sh or z, in most cases add “es” to make it plural. Examples are lunches or taxes. If a word ends in “y” and is preceded by a vowel, add “s” and if it is preceded by a consonant, change the “y” to “i” and add es. (Hmmm…a little trickier here, but still not too bad!) Some examples would be:
copy copies
key keys
When a word ends in “o” add s to make it plural if it is preceded by a vowel, such as ratio with the plural being ratios. However, when the “o” is preceded by a consonant you may have to add an “s” or “es” – check a dictionary for spelling. This includes words such as:
echo echoes
ego egos
If a noun ends in f, ef or ff you may simply add “s” or change the f or ef to “ve” and add s. (Getting a little harder here!) This rule applies to nouns such as:
belief beliefs
half halves
Some words form irregular words when pluralized and you may need to consult dictionary. For example we don’t use the word “womans” as a plural, we say “women” and child becomes “children.”
Some words are the same, whether they are singular or plural such as biceps, triceps, series or scissors.
When it comes to compound nouns, we pluralize single-word compounds as if the final word element stood alone. Therefore, the plural of backpack is backpacks (not backspack) and birthday is birthdays (not birthsday). For words that have a space between them or a hyphen, we pluralize the main noun. This includes words such as passerby, which becomes passersby or father-in-law with the plural being fathers-in-law.
If the compound word does not have a noun, we pluralize the final word element. So hang-up would be hang-ups and know-it-all becomes know-it-alls.
For words that end in “ful” make plural simply by adding “s.” We don’t change the “ful” to fulls. So the plural of teaspoonful is teaspoonfuls.
For proper nouns we add “s” to make it plural unless it ends in s, x, ch, sh or z in which case you would add es. Thus the name Smith becomes Smiths and Jones will be Joneses. We should keep the original spelling of proper nouns but add s or es depending on word ending. A couple of examples are Christmases and Rolexes.
Uppercase abbreviations are made plural by adding “s” (not apostrophe and s). This includes ECGs, IVs or MTs. Lower case abbreviations require an apostrophe and s to make them plural, such as c.o.d.’s or w.b.c.’s.
General Rules for Numbers
If we have a double-digit number we add an “s” and single-digit numbers are pluralized by adding apostrophe and s. Example: The patient who was in her 20s scored all 5’s on her physical assessment.
If numbers are expressed as words they are pluralized by adding s or es, such as ones or sixes.
Single letters are pluralized by adding apostrophe and s, such as A’s or B’s.
Summary Chart
| Singular Ending | Plural Ending | Applied Example of Rule |
| a | ae | Add letter e cava/cavae |
| ax | aces | Change x to ces thorax/thoraces |
| en | ina | Change en to ina foramen/foramina |
| is | es | Change is to es anastomosis/anastomoses |
| ix | ices | Change ix to ices appendix/appendices |
| ex | ices | Change x to ices apex/apices |
| on | a | Change on to a criterion/criteria |
| um | a | Change um to a ostium/ostia |
| us | i | Change us to i syllabus/syllabi |
| y | ies | Change y to ies cavity/cavities |
| ma | mata | Keep ma and add ta carcinoma/carcinomata |
Medical Transcription Exceptions
Some of the exceptions you may run into in medical transcription are listed below. Remember, many of the medical words we use are derived from Latin or Greek and thus the rules for English pluralization would not apply.
| Singular | Plural |
| arthritis | arthritides |
| calyx/calix c | alyces/calices |
| comedo | comedones |
| corpus | corpora |
| crus | crura |
| embryo | embryos |
| epididymis | epididymides |
| femur | femora |
| genius | geniuses |
| index | indexes |
| os | ora (meaning “mouth”) |
| os | ossa (meaning “bones”) |
| paries | parietes |
| pons | pontes |
| sinus | sinuses |
| vas | vasa |
| virus | viruses |
| viscus | viscera |
For Latin terms the adjective and noun must agree in gender, number, and case. There are many variations, and a medical dictionary is your best friend in deciphering these plurals. Some examples of singular to plural Latin medical words you might see are:
| Singular | Plural |
| verruca vulgaris | verrucae vulgares |
| pars interarticularis | partes interarticulares |
| nucleus pulposus | nucleus pulposi |
| musculus trapezius | musculi trapezii |
| chorda tendinea | chordae tendineae |
Latin Medical Terms (possessive case)
There are some Latin medical terms that are often misread as being plural when actually they are used in Latin to show the possessive case. Some of these are:
cervix uteri (neck of the uterus, uterine cervix)
corpus uteri (body of the uterus, uterine corpus)
pars uterina placentae (part of the placenta derived from uterine tissue)
pruritus vulvae (itching of the vulva)
os calcis: the plural is ossa calcium (bones of the heels)
