1. - is used at the end of a sentence to indicate a change and to express a definite tone of voice 2. - The particle "了" can also be used in the structure "要/快/就要/快要 +V/Adj+了" to indicate that the action is about to happen or that the situation is about to change. 3. - The negative adverbs "没有" and "了" cannot occur at the same time. For example, you can either say "我没吃早饭" or "我吃早饭了", not "我没吃早饭了". However, the verbs "没有" and "了" can appear at the same time, e.g.: "我没有钱了." 4.- Some adverbs that emphasise the late occurrence of an action cannot occur at the same time as "了", e.g. "刚、才、刚刚", etc. 5.-Adverbs that indicate that the action occurs frequently and "了" cannot occur at the same time, e.g. "经常、常常、每", etc.