Questions & Answers about Se o lobo viesse cá, nós fugíamos.
Why is the verb form viesse and not visse?
Viesse is the Imperfect Subjunctive (Pretérito Imperfeito do Conjuntivo) of the irregular verb vir (to come). It is very easy to confuse with visse, which is the exact same tense but for the verb ver (to see). Since the sentence means "If the wolf came here", we need viesse.
What triggers the use of the Subjunctive (Conjuntivo) in the first part of the sentence?
The word Se (If) sets up a hypothetical, unlikely situation. When you talk about a hypothetical condition like "If the wolf came...", Se always forces the following verb into the Imperfect Subjunctive tense.
Why use cá instead of aqui for "here"?
Why does the second half use the Imperfect past tense (fugíamos) instead of the Conditional (fugiríamos) to say "would run away"?
While you can absolutely use the Conditional (fugiríamos), everyday spoken Portuguese in Portugal usually replaces it with the Imperfect Indicative (fugíamos) in hypothetical "if" scenarios. Both mean "would run away" here, but the Imperfect is much more common and natural in casual conversation.