In this question I was asking about 曾经 and one answer says it means 'already'.
- What's the difference between 曾经 and 已经?
- Do the two sentences below have the same meaning?
I think it could be close to the fact to say "曾经(once)“ is used in the past tense, while "已经(already)" is used in the perfect(past, present, or future, it doesn't matter) tense, that's why ”了" is often used with it..
So when you are using the present perfect tense or future perfect tense, only 已经 can be used. For example(where 曾经 can't be used):
How about the past(past perfect) tense? As you may have learned in English. the past perfect tense implies that the fact the sentence is talking about is related to or affect the status quo, and the past tense just states a fact. That's true to "已经“ and "曾经". ALso, 曾经 could implies that the fact doesn't last till now(see my answer to a related question "What's the role of 曾经 in this sentence?") .For your examples:
Some other examples.
Let me show a conversation here. A policeman is investigating a case, and he is looking for a witness. He finds you and asks you some quesstions. You say,
Simply put, 曾经 indicates past tense while 已经 indicates perfect tense.
In other words, 曾经 means once while 已经 means already.