1. （变化或事件）早该发生的
    If you say that a change or an event is overdue, you mean that you think it should have happened before now.

    e.g. This debate is long overdue...
           这场辩论早该进行了。
    e.g. I'll go home and pay an overdue visit to my mother.
           我将回家看望母亲，其实我早该回去了。

2. （钱款）到期未付的，拖欠的
    Overdue sums of money have not been paid, even though it is later than the date on which they should have been paid.

    e.g. Teachers have joined a strike aimed at forcing the government to pay overdue salaries and allowances.
           教师加入了旨在迫使政府支付拖欠薪水和津贴的罢工。

3. （图书馆的书）逾期未还的
    An overdue library book has not been returned to the library, even though the date on which it should have been returned has passed.