The ball is in someone's court is a phrase commonly used to indicate that a decision or action is now up to someone else. There are several synonyms that can be used to convey the same idea, such as "the responsibility now lies with", "it's up to them to", "the onus is on", "it's in their hands now", "the outcome is now dependent on", "the fate rests with", and "the decision is now theirs to make". Whatever the phrase used, the underlying message is clear: the responsibility for what happens next rests with someone else. It's an important reminder that we all have control over our own choices and actions.
