ciertas

Ciértas is the feminine plural form of the Spanish adjective cierto, used as a determiner or modifier before feminine plural nouns. It signals that a specific subset within a larger set is being referred to, but the exact members are not fully enumerated in the sentence. The form agrees in gender and number with the noun it modifies, as in ciertas ideas, ciertas condiciones, and ciertas regiones.

Etymology and forms: cierto derives from Latin certus “certain.” Spanish maintains gendered forms: cierto (masculine singular), cierta (feminine singular), ciertos (masculine plural), and ciertas (feminine plural). While ciertas usually functions as a determiner, the word can also appear in predicative constructions when used with a noun as a descriptor.

Usage and nuance: ciertas emphasizes that the speaker has in mind a particular subset rather than a general or random selection. It is more specific than algunas in denoting a subset that is identified by context or prior discourse, though less forceful than determinate terms like determinadas. The choice between ciertas, algunas, or determinadas can affect nuance: ciertas implies a known or acknowledged portion; algunas is more neutral or indefinite; determinadas stresses precise, identifiable items.

Examples:

- Ciertas personas prefieren trabajar desde casa.

- En ciertas regiones, el clima es más extremo.

- La política de la empresa cubre ciertas condiciones.

- No todas las afirmaciones son ciertas; algunas son discutibles.

See also: cierto, cierta, ciertos, ciertas, determinaciones and cognates in other Romance languages (por ejemplo, portugues cert as).