文字装饰-线 | text-decoration-line

/* Keyword values */
text-decoration-line: none;
text-decoration-line: underline;
text-decoration-line: overline;
text-decoration-line: line-through;
text-decoration-line: blink;
text-decoration-line: underline overline;               /* Two decoration lines */
text-decoration-line: overline underline line-through;  /* Multiple decoration lines */

/* Global values */
text-decoration-line: inherit;
text-decoration-line: initial;
text-decoration-line: unset;

none | [ underline || overline || line-through || blink ]

<p class="wavy">Here's some text with wavy red underline!</p>
<p class="both">This text has lines both above and below it.</p>

.wavy { 
  text-decoration-line: underline;
  text-decoration-style: wavy;
  text-decoration-color: red;
}

.both {
  text-decoration-line: underline overline;
}