Know chalk from cheese informal verb phrase
To be able to distinguish between two individuals or objects (especially by recognizing their differences).
A: I quiz you. Which twin is Nam? B: I can know chalk from cheese. Nam has a birthmark on his neck, and Jack doesn't.
To have no influence on someone, either positive or negative.
1. Doing something extremely well
2. Behaving in an extreme or remarkable manner
1. Holly was in rare form during her speech, so she got the first prize in the competition last night.
2. Corrine: I'm going to buy Christmas presents for everybody. Do you want to go with me?
Laura: Oh...My kids are in rare form today, so I cannot go with you. Sorry!