"To some we bring pears at lunch, to others not."
Translation:Unora le aducem pere la prânz, altora nu.
In this case, unora is being used as a pronoun (instead of modifying a noun), so the pronoun form unora must be used. When unor is used as an adjective to modify a noun, then unor is the form that is used (in which case unor precedes the noun). In other words, here, we are saying, "to some" (pronoun use) instead of "to some pears" (adj use).