I could care less vs. I couldn't care less
I could care less和I couldn't care less已经被歪果仁自己说混了。到底哪个是在乎，哪个是不在乎呢？其实，I could care less表示你还是在乎的，不过只有那么一丁点；而I couldn't care less说得才是一点儿也不在乎。例如：Quite honestly, I couldn't care less what they do.（说实在的，他们做什么我真的无所谓。）
Saying that you could care less about a topic implies that you do care about it at least a little. What you usually mean is that you don’t care about the topic at all, hence “I couldn’t care less”.
Each one worse than the next vs. Each one worse than the last
“越来越”这样的说法很有趋向性，容易让人联想到将来。不过，它到底是在跟谁比？是与the next（下一个）还是the last（上一个）呢？选择用the next的小伙伴们，难道你们有预知未来的能力？！记住咯：越来越糟应该用each one worse than the last。
Unless you can foresee the future, “each one worse than the next” doesn’t make sense. The problem with this phrase is that it isn’t logical. For example, you can’t compare two bicycles until you’ve tested them both. So logically, you would compare the current bicycle to the last bike you tested.
On accident vs. By accident
都说学英语难，到底难在哪里？背不完的单词不说，介词搭配同样让人直呼头疼。就好比“故意地”英文是on purpose，“意外地”英文是by accident。所以，光记住一个孤零零的单词还不够，它和介词的万千搭配以及不同含义，也要准确地记住哟~ On accident这种说法，实在让英语学霸们不忍直视……
Sometimes I feel very sorry for people attempting to learn English. With phrases like this, it must be awful. You can do something on purpose, but not on accident. Prepositions are a killer.
For all intensive purposes vs. For all intents and purposes
也许你对要表达的观点反应很强烈，但for all intensive purposes这种说法不是正解。“总而言之”、“无论从哪点看”，英文是for all intents and purposes，这个短语还可以写成to all intents and purposes，如：The two items are, to all intents and purposes, identical.（这两个东西实际上是一样的。）
You may feel very strongly and intense about your purpose, but that doesn’t make the phrase correct. Another common incorrect use of the phrase is switching the words “for” and “with”. The correct phrase means that you are covering all possibilities and circumstances.
Irregardless vs. Regardless
Regard意思是“注意”、“考虑”，词尾加了 -less，表示“不管”，有一种藐视前方一切困难，勇往直前的气势，例如：It may rain, but I will go regardless.（有可能要下雨，但不管怎样我都要走。）Irregardless前面加了个“ir-”，这前后都加了否定，你到底是管还是不管呢？
Regardless means without regard. Throwing on “IR” to the beginning makes the word a double negative. I think we can all agree that “without without regard” doesn’t make sense.
360-degree change vs. 180-degree change
很多人爱说自己的人生有了360度的大转变。但是细细想来，360度是一个圈，这一转岂不是又转回来了？所以，形容转变180度就足够了，比如：I made a complete 180-degree change in my life.（我的人生发生了180度的大变化。）
People say they’ve made a complete 360-degree change in their life to imply that they’ve completely changed from the way they used to be. However, going 360 degrees means that you’ve returned to the exact same place you started. Which would mean you didn’t change at all. A 180-degree change would mean that you are the complete opposite which is what most people are trying to say.
Brothers-in-law vs. Brother-in-laws
If your wife or husband has several siblings, they’re called your “brothers/sisters in law”. The general rule of thumb for making a compound noun plural is to add a “s” to the noun that there’s more of. In our case, the words brother and law are both nouns. Since the word you’re pluralizing is brother, you add an “s” to it, not law.