ADJ [usually ADJ n] （规则、信息等）固定不变的，明确的 If you say that there are no hard and fast rules, or that there is no hard and fast information about something, you are indicating that there are no fixed or definite rules or facts. （规则、信息等）固定不变的，明确的
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There are no hard and fast rules, but rather traditional guidelines as to who pays for what.
关于谁来支付什么费用并没有明确的规定，只是遵循传统的准则罢了。
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At the moment there's no hard and fast timetable.
目前还没有明确的时间表。