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Forming Plurals of Medical Words

Forming proper plurals of medical words is one of the more challenging aspects of medical transcription. The problem is exacerbated by the fact that even dictating physicians frequently have difficulty with plurals. They cannot always be counted on to dictate the correct plural form. This pushes the burden of identifying and transcribing the proper plural straight back on the transcriptionist. The good news is that plurals generally follow some basic rules. Once you have mastered these rules, you will be able to quickly form proper plurals for most medical terms that you encounter. The bad news is that for every rule there is an exception. This means that you will also need to memorize (or look up) these exceptions. With practice you will become very familiar with all common plurals.
10 Common Exceptions to Basic Plural Rules: (note the “sometimes”)

1. Sometimes the proper plural of a word ending in is will be formed by dropping the “is” and adding “ides.” For example, “epididymis” becomes “epididymides.”
2. Sometimes the proper plural of a word ending in “us” will be formed by dropping the “us” and adding “era” or “ora.” For example: “viscus” becomes “viscera”; “corpus” becomes “corpora.”
3. Some words ending in “ix “or “ax” have more than one acceptable plural form. For example, the plural of “appendix” can be either “appendices” or “appendixes,” although the most common plural form would utilize the “ices” ending.
4. The proper plural for certain words ending in “ion” can be formed simply by adding an “s.” For example, “chorion” becomes “chorions.”
5. The plural form of the term “vas” is “vasa.”
6. The plural form of “pons” is “pontes.”
7. The plural form of the dual meaning word “os” is “ora” when referring to “mouths” and “ossa” when referring to “bones.”
8. The plural form of the term “femur” is “femora.”
9. The plural form of “cornu” is “cornua.”
10. The plural form of “paries” is “parietes.”

The chart below is designed to provide basic rules of thumb for forming plurals. But remember that there are exceptions to most of these rules.
If the
Singular Ending Is: Singular Example: The Plural Rule Is: Plural Form:
is diagnosis Drop the is and add es diagnoses
um ileum Drop the um and add a ilea
us alveolus Drop the us and add i alveoli
a vertebra Drop the a and add ae vertebrae
ix appendix Drop the ix and add ices appendices
ex cortex Drop the ex and add ices cortices
ax thorax Drop the x and add ces thoraces
ma sarcoma Drop the ma and add ta sarcomata
on spermatozoon Drop the on and add a spermatozoa
nx larynx Drop the x and add ges larynges
y deformity Drop the y and add ies deformities
yx calyx Drop the yx and add yces calyces
en foramen Drop the en and add ina foramina


A noted author of medical publications had this to say about Latin plurals:

Genitive (designating case that indicates possession or source) Forms/Derivations – Why plurals and possessives are sometimes so difficult.

Why does one use the Latin genitive form in the phrase “cyanosis retinae,” but prefer the anglicized form “retinas” to the Latin plural “retinae”? Genitive forms of Latin nouns occur in many medical phrases: abruptio placentae, cervix uteri, chrondromalacia patellae, etc. Physicians often misspell and mispronounce some of these, not sounding the last letter, “abruptio placenta-ee,” saying just “placenta.”

Certainly Latin words have become “naturalized” in English. Pluralized Latin words such as “curriculum, focus, lacuna” are commonly used without the Latin pluralizing: “curricula, foci, lacunae.” This group also includes Latin nouns whose singular and plural forms both end in “-es” (facies, pubes, series, species). In contrast, some Latin words are pleuralized by the addition of “s”: areas, arenas, auras, lumens, omens, specimens, or “-es,” “bonuses, calluses, lenses.”

One reason for treating Latin words under English rules is that the patterns for forming plurals are far more complex in Latin. For example, nouns that end in “-us” in the singular do not change in the plural (like English words “deer” and “salmon”), such as “arcus, decubitus, ductus, fetus, hiatus, ictus, introitus,” etc.

Because using the unaltered noun as a plural may cause confusion (“Some meatus are too small to admit even an 8 F catheter and all the above plexus are strictly motor”). Those words are best pluralized by the addition of “-es.” Although meatuses and plexuses may seem awkward to pronounce, they are preferable to the incorrect meati and plexi.

On becoming plural some words undergo vowel and consonant shifts, consonant insertions or a combination: appendix = appendices, cortex = cortices, dens = dentes, femur = femora, genus = genera. Failure to grasp how this process works results in forming incorrect singular words like phalanx = phalanges, but using phalange for the singular. Also, an interesting evolutionary process is the English translation process of adding a mispronounced final syllable, “eez” as in “abscesses” [abscess-eez], “interstices” [interstish-eez], “processes” [process-eez].

Some singular Latin nouns ending in “s” are often mistaken for plurals, (“obstetrical forceps consist of a left and a right blade” and “scabies are highly contagious”). Or incorrectly used without change as plural forms (“both biceps and quadriceps are symmetrical”). Singular nouns ending in “a” are also sometimes treated as plurals (“No stria were noted” and “lacuna are conspicuous in size and number”).

Conversely, Latin nouns that are chiefly or exclusively used in the plural are often mistaken for singular nouns, “adnexa, agenda, data, errata, fasces, fauces, feces, nares,” etc. Hence, such nouns are often used with singular verbs (The left adnexa is boggy and tender) or equipped with illegitimate endings to make them plural (both adnexae). These double plurals can also result from confusion regarding which form of a Latin noun is singular. Thus, the plurals, “diverticula, haustra” and “septa” are often mistaken for singulars and pluralized as “diverticulae” or “diverticuli,” “haustrae” and “septae” or “septi.”

The divergence of sense among current reference works (and reference sources often disagree) has almost certainly arisen from different assessments of patterns of usage among health professionals. The variations arise from uncertainty regarding the etymologic meanings of the words. For example, “hyphemia,” an abstract noun denoting a “condition of deficiency of blood” first became tangled with the Greek adjective “hyphaimos” (bruised, ecchymotic, suffused with blood). Then because the terms were often applied to hemorrhage in the anterior chamber of the eye where blood typically settles by gravity to form a crescent below the pupil, they were redefined as meaning “blood in a lower position.” The Greek prefix “hypo-” has been interpreted with no fewer than 4 related meanings: 1) beneath, 2) deficient, 3) slightly or to a lesser degree, 4) in a lower position.

Though confusing at times, you can see why what you hear and what you type are often difficult to decide.