Words wherein the Latin plural is the same as the Latin singular.
| (a) | Sing. | Plur. | (b) | Sing. | Plur. |
| Apparatus | apparatus | Caries | caries | ||
| Hiatus | hiatus | Congeries | congeries | ||
| Impetus | impetus | Series | series | ||
| Species | species | ||||
| Superficies | superficies. | ||||
SECOND CLASS.
Words wherein the Latin plural is formed from the Latin singular by changing the last syllable.
(a).—Where the singular termination -a is changed in the plural into -æ:—
| Sing. | Plur. | Sing. | Plur. |
| Formula | formulæ | Nebula | nebulæ |
| Lamina | laminæ | Scoria | scoriæ. |
| Larva | larvæ |
(b).—Where the singular termination -us is changed in the plural into -i:—
| Sing. | Plur. | Sing. | Plur. |
| Calculus | calculi | Polypus | polypi |
| Colossus | colossi | Radius | radii |
| Convolvulus | convolvuli | Ranunculus | ranunculi |
| Focus | foci | Sarcophagus | sarcophagi |
| Genius | genii | Schirrus | schirrhi |
| Magus | magi | Stimulus | stimuli |
| Nautilus | nautili | Tumulus | tumuli. |
| Œsophagus | œsophagi |
(c).—Where the singular termination -um is changed in the plural into -a:—
| Sing. | Plur. | Sing. | Plur. |
| Animalculum | animalcula | Mausoleum | mausolea |
| Arcanum | arcana | Medium | media |
| Collyrium | collyria | Memorandum | memoranda |
| Datum | data | Menstruum | menstrua |
| Desideratum | desiderata | Momentum | momenta |
| Effluvium | effluvia | Premium | premia |
| Emporium | emporia | Scholium | scholia |
| Encomium | encomia | Spectrum | spectra |
| Erratum | errata | Speculum | specula |
| Gymnasium | gymnasia | Stratum | strata |
| Lixivium | lixivia | Succedaneum | succedanea. |
| Lustrum | lustra |