如果某人非常高興，欣喜若狂就可以用 over the moon 這個短語，比喻一個人欣喜至極甚至都可以飛到月球上去。
If someone says you know your onions, it means you are experienced in something or you know a lot about a particular subject.
In English, if you take something with a pinch of salt, it means you don't believe it completely.
如果一件事情并不復雜，很容易理解或完成，那么就可以說 - 'it's not rocket science' 。
