1.burst out 侧重于突然爆发（声音）如：The class burst out laughing...； break out 侧重爆发（战争、疾病等）2.当“突然发生”时,两个词组用法没有区别.如：Then war burst out.战争突然爆发./ He was 10 years old when the war broke up.战争爆发时他只有10岁.