<div class="container">
  <h3>Lines break/wrap as they normally do, long words overflow their container</h3>
  <div class="text">
    <strong>pneumonoultramicroscopicsilicovolcanoconiosis</strong>   refers to a lung disease contracted from the inhalation of very fine silica particles,[8] specifically from a volcano; 
  </div>
</div>
<div class="container">
  <h3>Only overflowing words break using word-wrap/overflow-wrap</h3>
  <div class="text text-1">
    <strong>pneumonoultramicroscopicsilicovolcanoconiosis</strong>   refers to a lung disease contracted from the inhalation of very fine silica particles,[8] specifically from a volcano; 
  </div>
</div>
<div class="container">
  <h3>Both overflowing (long) words and words at end of lines break to fit lines</h3>
  <div class="text text-2">
    <strong>pneumonoultramicroscopicsilicovolcanoconiosis</strong>   refers to a lung disease contracted from the inhalation of very fine silica particles,[8] specifically <strong>from</strong> a volcano. </div>
</div>
body {
  background-color: #F5F5F5;
  color: #555;
  font-size: 1.1em;
  line-height: 1.5;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

.container {
  margin: 50px auto;
  max-width: 700px;
}

.text {
  padding: 20px;
  background-color: #0099cc;
  color: white;
  width: 300px;
  margin: 30px auto;
  text-align: justify;
  /*    box-sizing: border-box;*/
}

.text-1 {
  word-wrap: break-word;
  /* added this just to show that word-wrap has precedence over word-break */

  word-break: keep-all;
}

.text-2 {
  /* breaking words using word-break will also break words that would break using word-wrap */

  word-break: break-all;
}

strong {
  background-color: #006699;
}