Since與For的區別
The words since and for both deal with time. The two words are related to a duration or time period. Both words are prepositions (although since is also an adverb and a conjunction).
SInce和for的使用都與時間有關。這兩個詞都與時間段有關。兩個詞都是介詞（但since也是副詞和連詞）。
For example,
例如，
I have been teaching English for 10 years.
我教英語已經10年了。
or
或
I have been teaching English since 2007.
我從2007起開始教英語。
FOR:
The word for also sounds like the number 4. This reminds me of mathematics.
For聽起來也像是數字4的發音。這讓我想起了數學。
When you do the math (or calculate the amount of time) for the person then you use FOR.
當你爲某人計算數學題目（或計算時間）時，則使用FOR。
For example:
例如:
I have been waiting for 10 minutes.
我已經等了10分鐘了。
She has lived in the United States for 20 years.
她在美國住了20年。
He has been raising his hand for an hour.
他已經舉起了一個小時的手。
SINCE
:Since generally refers to the beginning of some period.
Since一般指的是指某一時期的開始
Let's look at some examples:
讓我們看一些例子：
She has been working out since 2:15pm.
她從下午2:15開始一直在工作。
They have been studying medicine since 2016.
他們從2016年以來就一直在學醫。
I have been living here since 2013.
我從2013年以來一直住在這裏。
I haven't seen Sarah since Friday.
自從星期五以來我就沒見過莎拉。
One last thing about since.
關於since的最後一點。
If you use the sentence, "It has been… (years or some time) then you MUST use since when using Present Perfect Verb Tense.
如果使用這個句子："It has been…（某年或某個時間）時，因爲該句爲現在完成時態時，所以必須使用since。
For example,
例如：
It has been 5 years since I quit smoking.
我戒菸已經5年了。
Next month, it will have been 4 years since I have been living in Brazil.
到下個月，我已經住在巴西4年了。
