il sopracciglio / le sopracciglia or i sopraccigli ("the eyebrow(s)") These nouns' endings derive regularly from the Latin neuter endings of the second declension (sg. -um / pl. -a), but there are some from the third declension as well: e.g. il gregge / le greggi (flock(s), but i greggi works, too); the tradition of calling them "irregular" or "mobile gender" (genere mobile) would come from the paradigm that there are so few nouns of this kind that the existence of neuter can be considered vestigial. The choice of plural is sometimes left to the user, while in some cases there are differences of meaning: Sometimes, for body parts, the feminine/neuter plural denotes the literal meaning while the masculine one denotes a figurative meaning: il braccio ("the arm") / le braccia ("the arms") / i bracci ("the isthmuses", "the inlets"); il corno ("the horn") / le corna ("the horns" of an animal) / i corni ("the horns" as musical instruments) Sometimes, especially in poetic and old-fashioned Italian, the masculine plural acts as a count noun, while the neuter/feminine plural acts as a mass noun: il cervello ("the brain") / due cervelli ("two brains") / le cervella ("the cerebral matter"); l'anello ("the ring") / due anelli ("two rings") / le anella ("ringlets"); furthermore, il dito ("the finger") / le dita ("the fingers") and also due dita ("two fingers") / but i diti indici ("the index fingers") Most noun stems are derived from the accusative: Latin socer/socerum begets Italian suocero, and Latin pēs/pēdem begets Italian piede. There are a few exceptions, however, such as uomo from Latin homo/hominem and moglie from Latin mulier/mulierem. Neuter third-declension nouns may bequeath Italian nouns either from the nominative/accusative case (e.g. capo from caput, cuore from cor) or from the oblique case used for other cases and for the plural (e.g. latte from lac, lact-, giure from ius, iur-). Irregular plurals There are a few genuine irregular plurals in Italian (plurali irregolari). Most of these were introduced in Vulgar Latin, but some derive from irregular Latin plurals. Examples include: (man/men; Latin ) (god(s); note also the irregularity in the article: gli instead of i) (ox(en); Latin ) (temple(s); the plural retains the l from Vulgar Latin in order to distinguish it from , the plural of ; the l is lost in the singular) Alteration In Italian, altered nouns are nouns with particular shades of meaning. They are