At this point you should already be familiar with the idea that English and Mandarin have distinct methods of representing the temporal relationship of actions. English uses “tense” while Mandarin uses “aspects”. In the English, the temporal relationship is represented by changing the “tense” of verbs, while Mandarin uses distinct grammar patterns using “aspect markers” such as 了(le), 的 (de), 过 (guo), etc.
Completed action 了
Completed action is something that was completed in the past.
Change of state 了
A change of state, in English is expressed with words like “now”, “anymore”, and “already”.
Details about completed actions 是 … 的
This pattern is used when the focus of the sentence is on “who”, “what”, “where” or “when”, rather than the action, which would have been established in a previous sentence. which