HD 203 Medical Terminology: Guidelines to Unusual Plural Forms

If the singular term ends in the suffix -a , the plural is usually formed by changing the ending to

-ae

example- bursa = bursae, vertebra = vertebrae

If the singular term ends in the suffix -ex or -ix , the plural is usually formed by changing these endings to

-ices

example- appendix = appendices, index = indices

If the singular term ends in the suffix -is , the plural is usually formed by changing the ending to

-es

example - diagnosis = diagnoses, metastasis = metastases

If the singular term ends in the suffix -itis , the plural is usually formed by changing the -is ending to

-ides

example- arthritis = arthritides, meningitis = meningitides

If the singular term ends in the suffix -nx , the plural is usually formed by changing the -x ending to

-ges

example-

phalanx = phalanges, meninx = meninges

If the singular term ends in the suffix -on , the plural is usually formed by changing the ending to

-a

example -

criterion = criteria, ganglion = ganglia

If the singular term ends in the suffix -um , the plural usually is formed by changing the ending to

-a

example -

diverticulum = diverticula, ovum = ova

If the singular term ends in the suffix -us , the plural is usually formed by changing the ending to

-i

example -

alveolus = alveoli, malleolus = malleoli