Lo peor ya ha pasado - Why is "Lo" used?

Question

The sentence translates to `The worse has already passed`. Why is `lo` used instead of `el`? When am I supposed to use one over the other?

Answer 1

You use lo because it is neutral. You do not know what the situationis that is the worst. If the situation is an accident (el accidente), then you would use el in place of the lo. If the situation was a sickness (la enferma), then la would replace the lo. Unless you know what the situation is, based on what was written earlier, the neutral lo is used. I hope this helps.