A bane is something that causes persistent trouble, misery, or harm. When something is the bane of your existence, it's a constant source of frustration or difficulty in your life. A student might say that long division is the bane of her math class, meaning it repeatedly trips her up and causes her grief.

The word carries a sense of ongoing struggle rather than a one-time problem. Mosquitoes might be the bane of a camping trip, showing up night after night to ruin outdoor fun. A coach might call turnovers the bane of his team's season if they keep losing games the same way.

Today, bane usually describes things that are annoying or harmful rather than actually deadly. Still, the word retains a dramatic quality. You wouldn't call a minor inconvenience a bane. When you describe something as your bane, you're saying it seriously interferes with your happiness or success, like how weeds can be the bane of a gardener's carefully tended vegetable patch, constantly returning no matter how many times they're pulled.