Metamorphosis metamorphoses
Parenthesis parentheses
Phenomenon phenomena
Radius radii _or_ radiuses
Stamen stamina
Seraph seraphim _or_ seraphs
Stimulus stimuli
Stratum strata
Thesis theses
Vertex vertices
Vortex vortices _or_ vortexes


[2] Genii, imaginary spirits: geniuses, persons of great mental
abilities.

[3] Indexes, when pointers or tables of contents are meant: indices,
when referring to algebraic quantities.

CASE.

Case, when applied to nouns and pronouns, means the different state,
situation, or position they have in relation to other words. Nouns have
three cases, the nominative, the possessive, and the objective.

I deem the essential qualities of _case_, in English, to consist, not in
the _changes_ or _inflections_ produced on nouns and pronouns, but in
the various offices which they perform in a sentence, by assuming
different positions in regard to other words. In accordance with this
definition, these cases can be easily explained on reasoning