The conditional mood in Russian is expressed with a complex
sentence that consist of a conditional clause and a subjunctive
clause.
The conditional clause begins with the conjunction если бы, followed by
the verb in the past tense.
The subjunctive clause has a verb in the past tense and the particle бы.
The sentence can begin with either clause:
Если бы у меня были деньги, я поехал бы на юг. If I had money, i would go to the south.
or,
Я поехал бы на юг, если бы у меня были деньги. I would go to the south, if I had money.
The conditional mood in Russian expresses
unreal conditions. The action in the subjunctive clause cannot take
place because the condition in the conditional clause cannot be
realized.
Russian also has conditional expressions with
conditional clauses that are realizable. These complex sentences do
not use the particle бы.
Я тебе позвоню, если ты будешь дома. I'll call you, if you are at home.
Если будет хорошая погода, мы поедем в парк. If the weather is nice, we'll go to the park.
In these sentences, the condition in the conditional clause upon which the
situation in the main clause depends is possible, realizable.