The 5th Declension is a very small group of Latin nouns, only a few of which have any influence on English. Most of these actually retain their Latin spelling as English derivatives; for example, species, series, and rabies. All these words have changed in pronunciation: Latin rabies (“rage,” “madness”) had three distinct syllables, “rah-bee-ace,” which we have reduced to two, “ray-bees.” Bona fides was a Latin phrase meaning “good faith”; we use it in that form, as well as in the Latin ablative case—bona fide (“in good faith”). In their nominative or vocabulary form, Latin 5th declension nouns always end in -es, and the base is the part of the word that precedes that ending.
|facies||form, face||series||row, series|
|rabies||rage, madness||species||look, appearance|
The base of faci-es appears in E facial. The origin of our word face, Latin facies suggested the “make” or “appearance” of a person. What is prima facie evidence? This word clearly had some semantic overlap with species, though species was less often used of the human countenance. English species (“spee-sheeze”) denotes the individual “appearance” of a variety of plant or animal life, as opposed to the broad class or genus. Its Latin plural is identical to the singular, as is the case with all 5th declension nouns.