ionic-framework/ionic/components/form/label.scss

// Label
// --------------------------------------------------

$input-label-color:         #888 !default;


.input-label {
  display: block;
  max-width: 200px;
  color: $input-label-color;
  font-size: inherit;
  white-space: nowrap;
}

.fixed-inline-label  {
  display: block;
  max-width: 200px;
  width: 30%;
  min-width: 100px;
  color: $input-label-color;
  font-size: inherit;
  white-space: nowrap;
}

.item-stacked-label {
  flex-direction: column;
  align-items: flex-start;

  .input-label {
    width: auto;
    max-width: 100%;
  }

  .input-label + .input {
    margin-top: 0;
  }
}

.item-floating-label {
  display: block;
  background-color: transparent;
  box-shadow: none;

  .input-label {
    position: relative;
    padding: 5px 0 0 0;
    opacity: 0;
    top: 10px;
    transition: opacity .15s ease-in, top .2s linear;

    &.has-input {
      opacity: 1;
      top: 0;
      transition: opacity .15s ease-in, top .2s linear;
    }
  }
}