使用overflow-wrap: break-word;如:

.yourelement{
  overflow-wrap: break-word;
}

Vincent Robert和Joey Adams的答案都是正确的。但是，如果您不想更改标记，可以使用javascript插入一个<br />。

在CSS中，不改变标记是无法做到这一点的。

<pre> <---------------------------------------
lorem ipsum
lorem ipsum
lorem ipsum
lorem ipsum
lorem ipsum
</pre> <--------------------------------------

OR

<div style="white-space:pre">  <-----------------------------------
lorem ipsum
lorem ipsum
lorem ipsum
lorem ipsum
lorem ipsum
</div>                         <-----------------------------------

来源:https://stackoverflow.com/a/36191199/2377343

使用overflow-wrap: break-word;如:

.yourelement{
  overflow-wrap: break-word;
}

要使元素在后面有换行符，为它赋值:

显示:块;

块级元素之后的非浮动元素将在下一行出现。许多元素，如<p>和<div>已经是块级元素，所以您可以只使用它们。

But while this is good to know, this really depends more on the context of your content. In your example, you would not want to use CSS to force a line break. The <br /> is appropriate because semantically the p tag is the the most appropriate for the text you are displaying. More markup just to hang CSS off it is unnecessary. Technically it's not exactly a paragraph, but there is no <greeting> tag, so use what you have. Describing your content well with HTMl is way more important - after you have that then figure out how to make it look pretty.

我喜欢非常简单的解决方案，这里还有一个:

<p>hello <span>How are you</span></p>

和CSS:

p {
  display: flex;
  flex-direction: column;
}