0
Semantic UI requires nothing out of the ordinary, da para aumentar o font size simply using a CSS class:
.cabecalho{
font-size: 250%;
}
<span class="cabecalho"></span>
If you want to give a check on some sizes predefined by Semantic UI itself, take a look here.
Here’s an example of a dropdown I found on the site itself:
<div class="ui selection dropdown">
<input type="hidden" name="gender">
<i class="dropdown icon"></i>
<div class="default text">Gender</div>
<div class="menu">
<div class="item" data-value="1">Male</div>
<div class="item" data-value="0">Female</div>
</div>
</div>
To change the font size of the items inside the drop, simply change the css class, just be careful that this code can change in other places using the class .item
also, any doubt leaves a comment here in my reply.
.item{
font-size:22px;
}