Sing. Plur. Formula formulæ Lamina laminæ Larva larvæ Sing. Plur. Nebula nebulæ Scoria scoriæ.
Sing. Plur.
Formula formulæ
Lamina laminæ
Larva larvæ
Sing. Plur.
Nebula nebulæ
Scoria scoriæ.

(b).—Where the singular termination -us is changed in the Plural into -i:—

Sing. Plur. Calculus calculi Colossus colossi Convolvulus convolvuli Focus foci Genius genii Magus magi Nautilus nautili Œsophagus œsophagi Sing. Plur. Polypus polypi Radius radii Ranunculus ranunculi Sarcophagus sarcophagi Schirrhus schirrhi Stimulus stimuli Tumulus tumuli.
Sing. Plur.
Calculus calculi
Colossus colossi
Convolvulus convolvuli
Focus foci
Genius genii
Magus magi
Nautilus nautili
Œsophagus œsophagi
Sing. Plur.
Polypus polypi
Radius radii
Ranunculus ranunculi
Sarcophagus sarcophagi
Schirrhus schirrhi
Stimulus stimuli
Tumulus tumuli.

(c).—Where the Singular termination -um is changed in the Plural into -a:—

Sing. Plur. Animalculum animalcula Arcanum arcana Collyrium collyria Datum data Desideratum desiderata Effluvium effluvia Emporium emporia Encomium encomia Erratum errata Gymnasium gymnasia Lixivium lixivia Lustrum lustra Sing. Plur. Mausoleum mausolea Medium media Memorandum memoranda Menstruum menstrua Momentum momenta Premium premia Scholium scholia Spectrum spectra Speculum specula Stratum strata Succedaneum succedanea.
Sing. Plur.
Animalculum animalcula
Arcanum arcana
Collyrium collyria
Datum data
Desideratum desiderata
Effluvium effluvia
Emporium emporia
Encomium encomia
Erratum errata
Gymnasium gymnasia
Lixivium lixivia
Lustrum lustra
Sing. Plur.
Mausoleum mausolea
Medium media
Memorandum memoranda
Menstruum menstrua
Momentum momenta
Premium premia
Scholium scholia
Spectrum spectra
Speculum specula
Stratum strata
Succedaneum succedanea.

(d).—Where the singular termination -is is changed in the Plural into -es:—

Sing. Plur. Amanuensis amanuenses Analysis analyses Antithesis antitheses Axis axes Basis bases Crisis crises Diæresis diæreses Sing. Plur. Ellipsis ellipses Emphasis emphases Hypothesis hypotheses Oasis oases Parenthesis parentheses Synthesis syntheses Thesis theses.
Sing. Plur.
Amanuensis amanuenses
Analysis analyses
Antithesis antitheses
Axis axes
Basis bases
Crisis crises
Diæresis diæreses
Sing. Plur.
Ellipsis ellipses
Emphasis emphases
Hypothesis hypotheses
Oasis oases
Parenthesis parentheses
Synthesis syntheses
Thesis theses.

THIRD CLASS.

Words wherein the Plural is formed by inserting -e between the last two sounds of the singular, so that the former number always contains a syllable more than the latter:—

Sing. Plur.
Apex sounded apec-s apices
Appendix — appendic-s appendices
Calix — calic-s calices
Cicatrix — cicatric-s cicatrices
Helix — helic-s helices
Index — indec-s indices
Radix — radic-s radices
Vertex — vertec-s vertices
Vortex — vortec-s vortices.