to be knowledgeable or skilled about something
对某事有知识或技能 (duì mǒu shì yǒu zhīshi huò jìnéng)
"You can tell she really knows her stuff about physics."
"你可以说她对物理学真的很了解。" (Nǐ kěyǐ shuō tā duì wùlǐxué zhēn de hěn liǎojiě.)
using influence to get something done
To stay calm and steady, especially during difficulties.
an outstanding work of art or achievement
to improve or advance to a higher level
experiencing a period of bad luck
the most vulnerable part of a system or group
