英语句法层面有这些1. 对等连接词 coordination conjunctions 有七个，可用fanboys来记： and but so or nor for yet
2. 配对连接词 correlative conjunctions 有五个:both …andnot only … but alsoeither … orneither … norwhether …or。
这些对等词连接两个字或片语的时候不须要逗号。应特别注意平行结构，也就是对等词的两边词性必须一致。 Would you rather take a written or an oral exam?The system is not only plicated but also inefficient.对等词也可以连接两个子句， 必须用逗号将两个句子分开。S + VCC S + V.I was feeling hungry so I made myself a sandwich.3.从属词subordinator从属连接词subordinating conjunction 是带领副词子句的连接词，如although when while before after because if as等。它会放在非子句dependent clause的句首，带领子句与非子句结合成一个完整的句子。非子句在前面的时候需要用逗号分开两个子句，假如是子句在前面，因为有从属连接词明显地把两个子句分开，所以不用逗号。SC + S + VS + V. or S + V + SC + S + V.Because I was feeling hungryI made myself a sandwich.I made myself a sandwich because I was hungry.4.转折字，转折片语与连接副词trition words and phrases and conjunctive adverbs转折字，转折片语与连接副词不像从属词的位置那样固定，他们可以放在子句的句首，句中，句尾，而且通常会用逗号分开来。S + V; CAS + V. or S + V. CAS + V.I was feeling hungry; thereforeI made myself a sandwich.I was feeling hungry. ThereforeI made myself a sandwich.I was feeling hungry. I made myself a sandwichtherefore.I was feeling hungry. Ithereforemade myself a sandwich.5.其他others有一些其他的名词如example，形容词如additional，副词如too，介系词片语如in addition to，动词如cause等也可以用来表示转折语。这些次没有特定的标点符号规则，必须注意前后的字词的用法。An additional reason for visiting Taipei is its convenience.1.becuase(因为）e.g. Carol is clever because she is kind.2.and（和） e.g. Melissa is beatiful and clever.3.but（但是） e.g. The old man is hungry but he no money to buy food.4.or（或者） e.g. Do you want to stay at home or go shoppong?
