英文簡短解釋?

Black sheep：
A member of a family or other group who is considered undesirable or disreputable
This metaphor is based on the idea that black sheep were less valuable than white ones because it was more difficult to dye their wool different colors. Also, in the 16th century, their color was considered the devil's mark.

Rule of thumb：
A rule of thumb is a basic rule that is usually but not always correct.
Another possibility is a term dating back to medieval times when the diameter of your thumb was the largest diameter of stick that was allowable for disciplining one's wife.

Black sheep:
1. A sheep with black fleece.
2. A member of a family or other group who is considered undesirable or disreputable.

Rule of thumb:
1. refers to shortcuts to solutions to new problems that resemble problems previously solved by experienced workers.
2. A useful principle having wide application but not intended to be strictly accurate or reliable in every situation.