How to style dt and dd so they are on the same line?

Question

dl {
  width: 100%;
  overflow: hidden;
  background: #ff0;
  padding: 0;
  margin: 0
}
dt {
  float: left;
  width: 50%;
  /* adjust the width; make sure the total of both is 100% */
  background: #cc0;
  padding: 0;
  margin: 0
}
dd {
  float: left;
  width: 50%;
  /* adjust the width; make sure the total of both is 100% */
  background: #dd0;
  padding: 0;
  margin: 0
}

<dl>
  <dt>Mercury</dt>
  <dd>Mercury (0.4 AU from the Sun) is the closest planet to the Sun and the smallest planet.</dd>
  <dt>Venus</dt>
  <dd>Venus (0.7 AU) is close in size to Earth, (0.815 Earth masses) and like Earth, has a thick silicate mantle around an iron core.</dd>
  <dt>Earth</dt>
  <dd>Earth (1 AU) is the largest and densest of the inner planets, the only one known to have current geological activity.</dd>
</dl>

I have got a solution without using floats!
check this on codepen

Viz.

dl.inline dd {
  display: inline;
  margin: 0;
}
dl.inline dd:after{
  display: block;
  content: '';
}
dl.inline dt{
  display: inline-block;
  min-width: 100px;
}

Update - 3^rd Jan 2017: I have added flex-box based solution for the problem. Check that in the linked codepen & refine it as per needs.

dl.inline-flex {
  display: flex;
  flex-flow: row;
  flex-wrap: wrap;
  width: 300px;      /* set the container width*/
  overflow: visible;
}
dl.inline-flex dt {
  flex: 0 0 50%;
  text-overflow: ellipsis;
  overflow: hidden;
}
dl.inline-flex dd {
  flex:0 0 50%;
  margin-left: auto;
  text-align: left;
  text-overflow: ellipsis;
  overflow: hidden;
}

CSS Grid layout

Like tables, grid layout enables an author to align elements into columns and rows.
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Grid_Layout

To change the column sizes, take a look at the grid-template-columns property.

dl {
  display: grid;
  grid-template-columns: max-content auto;
}

dt {
  grid-column-start: 1;
}

dd {
  grid-column-start: 2;
}

<dl>
  <dt>Mercury</dt>
  <dd>Mercury (0.4 AU from the Sun) is the closest planet to the Sun and the smallest planet.</dd>
  <dt>Venus</dt>
  <dd>Venus (0.7 AU) is close in size to Earth, (0.815 Earth masses) and like Earth, has a thick silicate mantle around an iron core.</dd>
  <dt>Earth</dt>
  <dd>Earth (1 AU) is the largest and densest of the inner planets, the only one known to have current geological activity.</dd>
</dl>

If you use Bootstrap 3 (or earlier)...

<dl class="dl-horizontal">
    <dt>Label:</dt>
    <dd>
      Description of planet
    </dd>
    <dt>Label2:</dt>
    <dd>
      Description of planet
    </dd>
</dl>

Assuming you know the width of the margin:

dt { float: left; width: 100px; }
dd { margin-left: 100px; }