Etymology: < classical Latin -a, ancient Greek -α, nominative ending of nouns of the first declension (usually feminine in Latin, always so in Greek). Compare -ia suffix¹.-a of this origin occurs in many loanwords < classical Latin, post-classical Latin, and ancient Greek (generally technical in origin, though in many cases later entering ordinary use), as mandragora n., manna n.¹ (Old English), asafœtida n., boa n., idea n. (Middle English), alga n., area n., peninsula n. (mid 16th cent.), rota n. (early 17th cent.), arena n., catena n., corolla n., lamina n., larva n., nebula n. (mid 17th cent.), antenna n., formula n. (late 17th cent.), camera n. (18th cent.). Some words of this class have an earlier parallel form borrowed (in Middle English or the 16th cent.) from French with final -e that was subsequently either assimilated to or supplanted by the later borrowing of the Latin or Greek form, compare e.g. chimera n., hyena n., vertebra n. In Old English learned borrowings from the Latin first declension generally became either weak feminine nouns (in -e ) or strong masculine nouns (without an ending in the nominative); however, several words (chiefly, but not exclusively, masculine in Latin) were assimilated to the weak masculine declension (in -a ); see further A. Campbell Old Eng. Gram. (1959) §560. In many cases -a in these words was in Middle English weakened to -e or lost altogether, as Old English comēta comet n., crisma chrism n., pāpa pope n.¹, prophēta prophet n. The suffix is frequently employed in scientific Latin formations, of which the first element may be an appropriate classical Latin or ancient Greek word or (especially in genus names) a proper name, e.g. lavatera n. (mid 18th cent.), amoeba n. (mid 19th cent.), colea n. (early 20th cent.). In the names of metallic oxides, the suffix was used on the pattern of soda n.¹ to form terms such as alumina n. (late 18th cent.) and potassa n. (early 19th cent.), but later examples may be regarded as having been formed with -ia suffix¹ (perhaps after magnesia n.) in parallel with element names in -ium suffix: e.g. yttria n.

Etymology: < classical Latin -a, ancient Greek -α, nominative and accusative plural ending of neuter nouns (with singulars ending, respectively, in -um and -ον).Several early borrowings of words of this class (16th–17th cent.) are first attested in the plural -a form and in some cases a ‘double’ plural in -as is the earliest or an early form, compare datum n., erratum n., minimum n., phenomenon n., scholium n. Conversely, many 16th- and 17th-cent. loanwords in -on or -um do not regularly show a plural form in -a until the 18th or 19th cent., e.g. compendium n., cranium n., emporium n., maximum n., spectrum n., speculum n. With borrowings from the mid 17th cent. onwards the -on or -um singular and -a plural tend to be attested in the same period, e.g. bacterium n., criterion n., desideratum n., effluvium n. In current usage -a remains the norm as the plural of many technical words (although often varying with -ums or -ons ); for words in ordinary use there is much competition between the rival plural forms (the choice frequently depending on variety or register), compare e.g. consortium n., gymnasium n., memorandum n., podium n., referendum n., although the general trend is away from-a , which in some cases is now very rare or archaic, e.g. museum n., pentathlon n. The tendency to treat the plural -a ending as if it were a singular (compare -a suffix¹) remains strong in all periods, compare e.g. addendum n., candelabrum n., erratum n., phenomenon n. Some words in -a that are borrowings of such Latin and Greek plurals are used only in the plural or in some cases have become singular, e.g. impedimenta n. (17th cent.), rariora n., tacenda n. (19th cent.), agenda n., media n.² (20th cent.). Probably based on these are a small number of collective formations on adjectives in -ic suffix, denoting subjects of discourse and collections of items, e.g. aeronautica n. (mid 18th cent.). Frequently used to form scientific Latin plural names of classes or groups of animals, as Mollusca n. (17th cent.), Crustacea n. (19th cent.), of which the singular is variously supplied by mollusc n., crustacean n., etc.; in some instances these group names represent the plural form of a genus name, e.g. Podophthalma n.