Rules for singular/plural
Term ending in a:
Drop a and add ae
Term ending in is:
Drop is and add es
Term ends in nx:
Drop nx add nges
Term ends in um:
Drop um add a
Term ends in us:
Drop us add i
Term ends in y:
Drop y add ies
Vertebra = vertebrae
Diagnosis = diagnoses
Phalanx = phalanges
Bacterium = bacteria
Digitus = digiti
Therapy = therapies