句子副词用于修饰句子(而不是修饰某个单个的词)，反映说话人的观点和看法，如 actually, apparently, certainly, clearly, definitely, evidently, fortunately, frankly, honestly, luckily, obviously, perhaps, possibly, probably, surely, undoubtedly, unexpectedly 等。
二、句子副词在句中的位置
句子副词通常位于句首(或分句句首)。如：
Obviously he can't tell the difference between them. 显然他无法区别两者的不同。
I arrived late but luckily the meeting had been delayed. 我迟到了，幸而会议推迟了。
但有些句子副词也可以出现句中。如：
He smiled nastily. He evidently knew something I didn't. 他发出狞笑，他显然知道一些我所不知道的事。
有的句子也可用作其他种类的副词，不过这往往会导致位置和语义的变化：
Clearly he didn't say so. 显然他没有这样说。(句子副词)
He didn't say so clearly. 他说得没有那么清楚。(方式副词)
Frankly, you are wrong. 说实在的，你错了。(句子副词)
He spoke frankly about his past life. 他坦率地谈了他过去的生活。(方式副词)
Seriously, I really think he likes you. 真的，我的确认为他喜欢你。(句子副词)
I have never seriously thought about it. 我从未认真考虑过它。(方式副词)
