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Bootstrap class: .carousel-caption

<div class="bd-example">
  <div id="carouselExampleCaptions" class="carousel slide" data-ride="carousel">
    <ol class="carousel-indicators">
      <li data-target="#carouselExampleCaptions" data-slide-to="0" class="active"></li>
      <li data-target="#carouselExampleCaptions" data-slide-to="1"></li>
    </ol>
    <div class="carousel-inner" role="listbox">
      <div class="carousel-item active">
        <img class="d-block w-100" src="/placeholder/pictures/image.svg" alt="First slide">
        <div class="carousel-caption d-none d-md-block">
          <h3>First slide label</h3>
          <p>Nulla vitae elit libero, a pharetra augue mollis interdum.</p>
        </div>
      </div>
      <div class="carousel-item">
        <img class="d-block w-100" src="/placeholder/pictures/image.svg" alt="Second slide">
        <div class="carousel-caption d-none d-md-block">
          <h3>Second slide label</h3>
          <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
        </div>
      </div>
    </div>
    <a class="carousel-control-prev" href="#carouselExampleCaptions" role="button" data-slide="prev">
      <span class="carousel-control-prev-icon" aria-hidden="true"></span>
      <span class="sr-only">Previous</span>
    </a>
    <a class="carousel-control-next" href="#carouselExampleCaptions" role="button" data-slide="next">
      <span class="carousel-control-next-icon" aria-hidden="true"></span>
      <span class="sr-only">Next</span>
    </a>
  </div>
</div>

Preview

Sass source

/* _carousel.scss:226 */
.carousel-caption {
  position: absolute;
  right: ((100% - $carousel-caption-width) / 2);
  bottom: 20px;
  left: ((100% - $carousel-caption-width) / 2);
  z-index: 10;
  padding-top: 20px;
  padding-bottom: 20px;
  color: $carousel-caption-color;
  text-align: center;
}

Uses variables

/* _carousel.scss:226 */
$carousel-caption-width
$carousel-caption-width
$carousel-caption-color