Singular

-a

Plural

Retain a and add e.

ex. pleura to pleurae

Singular

-ax

Plural

Drop x and add ces.

ex. thorax to thoraces

Singular

-en

Plural

Drop en and add ina

ex. lumen to lumina

Singular

-is

Plural

Drop is and es

ex. diagnosis to diagnoses

Singular

-ix

Plural

Drop ix and add ices

ex. appendix to appendices

Singular

-ex

Plural

Drop ex and add ices

ex. apex to apices

Singular

-ma

Plural

Retain ma and add ta

ex. carcinoma to carcinomata

Singular

-on

Plural

Drop on and add a

ex. ganglion to ganglia

Singular

-um

Plural

Drop um and add a

ex. bacterium to bacteria

Singular

-us

Plural

Drop us and add i

ex. bronchus to bronchi

Singular

-y

Plural

Drop y and add ies

ex. deformity to deformities