Definition: The subjunctive mood is an especially form of verb that helps us to express our desires, because with the subjunctive mood we can express wishing, feelings, assumptions, doubts, dreams and speculations. For that you can write a verb in subjunctive mood in Russian language you must put the word бы (by) near of the verb or in somewhere of sentence.
Examples:
She would have passed the course if she had studied.
Она прошла бы конечно, если ее изучали.
Ona proshla bykonechno, yesli yee izuchali.
I would have played football if I was not sick.
Я бы играл в футбол, если бы я не был болен.
YA by igral v futbol, yesli by ya ne byl bolen.
If we would have lunch, we should not be hungry.
Если мы хотим пообедать, нас не должно быть голодным.
Yesli my hotim poobedatʹ, nas ne dolzhno bytʹ golodnym.
He would have been eating all night
Он бы ел всю ночь
On by yel vsyu nochʹ
They would play all day.
они играли бы весь день.
oni igrali by vesʹ denʹ.
You would have won if not for that mistake.
Вы выиграли бы, если бы не эта ошибка
Vy vyigrali by, yesli by ne eta oshibka.