Singular and plural endings of some scientific terms:

Singular            Plural                    Examples:
                                                        Singular                            Plural

-um, -on            -a                        Cilium/Mitochondrion      Cilia/Mitochondria      
-en                    -ina                      Foramen                         Foramina
-a                      -ae or -ata           Larva/Stoma                   Larvae/Stomata
-ur                    -ora                      Femur                             Femora
-us                     -i (or -ora, -ura)  Nucleus/Corpus/Crus      Nuclei/Corpora/Crura
-is                      -es                      Taxis/Symphysis              Taxes/Symphyses
-ex, -ix               -ices                    Matrix                            Matrices 
-yx                    -yces                   Calyx                              Calyces
-anx                  -anges                  Phalanx                           Phalanges
-inx                   -inges                   Meninx                           Meninges

Notice that the "-a" ending is both a singular and a plural ending, and, as such, is notoriously
confusing.  You must simply learn which ending goes with which words.

For instance, note that it is one mitochondrion and many mitochondria.

On the other hand, it is one larva or pupa and many larvae or pupae.

Be aware as well that you would never write mitochondriae -- that would be a plural of a plural,
    and there is no such thing! 

 Faculty Index Page  Dr. James K. Adams - 148 Sequoya Hall;