名詞 unknown quantity:

1. a factor in a given situation whose bearing and importance is not apparent
2. a variable whose values are solutions of an equation
   同義詞：unknown

1. The new teacher is still very much an unknown quantity but we have hopes that he will be a valuable member of our team.
   新教師是誰現(xiàn)在還難以預料，但我們希望他會成為我們隊里的重要一員。
2. The new sales director is still a bit of an unknown quantity.
   新來的銷售部主任大家還不大了解。