规则8 用破折号引出突然的停顿或中断，并引出较长的同位语或总结[rule-8]

破折号是一种比逗号更强的分隔标记，不如冒号正式，比圆括号更放松。

• His first thought on getting out of bed—if he had any thought at all—was to get back in again.
• The rear axle began to make a noise—a grinding, chattering, teeth-gritting rasp.
• The increasing reluctance of the sun to rise, the extra nip in the breeze, the patter of shed leaves dropping—all the evidences of fall drifting into winter were clearer each day.

只有当更常见的标点符号显得不够用时，才使用破折号。

• 误：Her father's suspicions proved well-founded. It was not Edward she cared for, it was San Francisco.
• 正：Her father's suspicions proved well-founded—it was not Edward she cared for—it was San Francisco.

• 误：Violence, the kind you see on television, is not honestly violent. There lies its harm.
• 正：Violence—the kind you see on television—is not honestly violent—there lies its harm.