1. after-thought 与 second thought

after-thought 是指不是原来计划的（not originallyplanned）；但是 second thought 是表示再考虑，也许还会改变主意（think itover; may change mind）。

例句：
(1) The manager said that the new product was an after thought.
（经理说那新产品不是原来计划内的事。）

(2) Let me have a secondthought.（让我再考虑一下。）

至于 second opinion，意思是「另外意见」。

例句：He would like to have a second opinion from another laywer.（他要听听另一位律师的意见。 ）

2. block out 与 black out

block out 意思是草拟大纲或订出某种计划，drew up的意思。
例句：Her boss prefers her to block out her annua plan.（老板要她订出年度计划。）

black out指停电（power off）
例句：There was a black out in our office yesterday.（昨天办公室停电。）（当名词用）

3. call someone names 与 call one's name

call someone names是指「骂人」或「侮辱」，有一点像中文讲指名道姓一样；注意，names用复数；call someone's name是指「呼喊某人的名字」，call 后面是用名词或代名词的所有格（即his, your, our 等），而且 name 不加s。

例句：
(1) He called her（bad）names. 他骂她。（bad也可省略，写成 name-calling 时，name 用单数）
(2) I called his name in the supermarket.（我在超市叫他的名字）或：I called him by his name.

4. economic和economical

economic意为"经济上的、与经济有关的"；economical意为"节约的、节省的"。例句：
(1) The present economic situation in Italy isserious.（目前意大利的经济状况很不乐观。）
(2) I have to be economical because I don't have much money. 我要节省一点，因为我钱不多。