<fieldset>
  <div class="form-inline" style="margin-bottom:10px;">

    <div class="form-group">
      <%= f.text_field "synonyms[value]", class: "form-control" %>
    </div>

    <div class="form-group">
      <%= f.text_field "synonyms[synonyms]", class: "form-control", style: 'width: 300px;' %>
    </div>

    <%= f.hidden_field :destroy %>

    <button class="btn btn-default remove_fields">X</button>
  </div>
</fieldset>