Verbs Following Si Often in Subjunctive Mood

Most clauses that begin with si (the equivalent of "if") are what is known as conditional clauses. Which verb you use as part of that clause depends a great deal on how likely you believe the condition to be true. Thus a clause such as si yo fuera tú ("if I were you") uses an imperfect subjunctive verb because it's not likely to be true. (In this example, note that the English also uses the subjunctive.) This concept is further explained in our lesson on clauses beginning with si.