“了”表发生或完成 "了"Indicating Occurrence or Completion

“了”用于句尾。例如：
"了" can be used at the end of a sentence. For example:

“了”用于动词后带宾语。动词后的宾语前面一般要有定语，如数量词或形容词、代词等。例如：
"了" can also be used between a verb and its object. There is usually a modifier before the object of the verb, such as a numeral classifier, an adjective or a pronoun, etc. For example:

上述两种用法的“了”的否定形式是：“没+动词（+宾语）”，“了”要去掉。例如：
The negative form of "了" in both cases above is "没+verb（+object）". In the negative form, "了" should be omitted. For example:

“了”用于句末，表示变化或新情况的出现。
"了" is used at the end of a sentence to indicate a change or the occurrence of a new situation.