有一些短语在公开课里经常会被用到，在这里把它们记录下来，这里面有一些是计算机科学的行话（jargon），也有一些通用的的短语。
行话
trivial 与 non - trivial
刚接触 trivial 这个词时刚到有些困惑，感觉有时候意思是简单，有时候意思是不重要，而词典的解释是
adj.琐碎的；不重要的；微不足道的
If you describe something as trivial, you think that it is unimportant and not serious.计算机的教授喜欢说 trivial 和 non - trivial，trivial 表示一个问题的解决方法很明显，比如输入一个数组找出数组的最大值，non - trivial 表示一个问题的答案不是那么明显，要想真正搞明白需要进行一些思考，比如红黑树。
通用短语
from scratch
从零开始；从头做起；白手起家
If you do something from scratch, you do it without making use of anything that has been done before.wrap up
圆满完成，圆满结束(工作、协议等)
If you wrap up something such as a job or an agreement, you complete it in a satisfactory way.结束的时候老师可能会说 let’s wrap up today’s class with blahblah
rule of thumb
(根据实际经验的)粗略估算；经验之谈
A rule of thumb is a rule or principle that you follow which is not based on exact calculations, but rather on experience.根据经验来的准则，没有被证明过，但一般都是这样
hold
（命题定理等）成立，如 x ^ 2 is no less than 0, but it’ll not hold if x is an imaginary number.punch line
妙处
the final phrase or sentence of a joke or story, providing the humor or some other crucial element.基本上意思就是重要之处
- takeaway
这个词在公开课的语境下不是外卖的意思。。。 takeaway 就是重点a key fact, point, or idea to be remembered, typically one emerging from a discussion or meeting.