<div class="collapse navbar-collapse" id="navbarColor01">
  <ul class="navbar-nav mr-auto">
    <li class="nav-item active">
      <a class="nav-link" href="index.html">Applications<span class="sr-only">(current)</span></a>
    </li>
    <li class="nav-item">
      <a class="nav-link" href="wiki.html">Wiki</a>
    </li>

    <li class="nav-item dropdown">
        <a class="nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button" aria-haspopup="true" aria-expanded="false">Dropdown</a>
        <div class="dropdown-menu">
          <a class="dropdown-item" href="#">Action</a>
          <a class="dropdown-item" href="#">Another action</a>
          <a class="dropdown-item" href="#">Something else here</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="#">Separated link</a>
        </div>
    </li>

  </ul>

</div>