Latin plurals used in the English language

An excerpt from an article at Macmillan Dictionary:

English constantly imports words from other languages, and over time these loan words can become thoroughly anglicised and may therefore be pluralised in the usual English ways: typically by adding -s or -es. Persona retains its Latin flavour and so the Latin plural personae survives, though some restrict it to literary and technical contexts. The anglicised plural personas is also frequently seen; indeed, both forms are on the rise.

The two spellings’ coexistence – some call it competition – is not unusual: witness appendixes and appendices, formulas and formulae, millenniums and millennia, referendums and referenda, stadiums and stadia, and thesauruses and thesauri, all used regularly...

There are no hard and fast rules about which plural to use and when. In certain cases the Latin is more formal or even affected, but not predictably so. Occasionally the two spellings differentiate in meaning. For example, stigmata normally implies a religious context, while stigmas is the general-purpose plural. Some authorities advise limiting mediums to spiritualists and using media for all other senses of the word, but usage varies.

More at the link, via Sentence First.