hang out 出去玩，閑逛

errand n. 差事，跑腿
I've got a few errands to do in the town.
我有幾件事要進城辦。
You must do the two errands this week.
你必須在一周內(nèi)完成這兩項任務。
My mother asked me to go on an errand; she wanted me to buy some food.
我媽媽叫我跑一下腿,她想讓我去買點食物。

calculus n. 微積分
It's been awhile since I did calculus.
我學微積分已經(jīng)有一段時間了。
I had studied calculus before I got into college.
我在上大學以前,已經(jīng)學過微積分。

up to par adj. 達到水平(正常)
I didn't think her performance was up to par.
我認為她表現(xiàn)得不及平時。

unbelievable adj. 難以置信的
They work with an unbelievable speed.
他們以令人難以置信的速度工作。
His ecstasy to the pop music is unbelievable.
他對流行音樂的入迷是令人難以置信的。

convention n. 慣例
The handshake is a social convention.
握手是社交慣例。

start over v. 重新開始
I suggest that you tear up the letter and start over again.
我建議你把這封信撕了，再重頭開始寫。