括号
①解释说明生词;②补充说明
Drugs (substances) that affect the central nervous system and alter perception, mood, and behavior are known as psychoactive substances. (1997，Text 3)
8、破折号
①一个破折号后面起补充说明或评价判断。
I am an idiot - the stupidest kind of all。
"This book stands for reason itself。" And so it does - and all would be well were reason the only judge in the creationism/evolution debate。
②两破折号之间其补充说明，可先跳过不看。
In Australia-where an aging population, life-extending technology and changing community attitudes have all played their part-other states are going to consider making a similar law to deal with euthanasia。
