unknown quantity

名词 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
   同义词：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.
   新教师是谁现在还难以预料，但我们希望他会成为我们队里的重要一员。
2. The new sales director is still a bit of an unknown quantity.
   新来的销售部主任大家还不大了解。