[[LuaTeX]] and [[MkIV]] allow advanced usage and manipulation of [[Open Type]] <i>open-type features</i>. Some features, such as <i>onum</i> (oldstyle) and <i>smcp</i> (smallcaps) are known to most users of Open Type fonts, and virtually every open type font has default features for kerning (<i>kern</i>) and ligatures (<i>liga</i>). More advanced OT fonts can have lots more, including the Stylistic Set feature <i>ss<nn></i> (where <i>nn</i> stands for any numeral between 01 and 99).
% Let's reset and get the original default set back and add smallcaps:\startX A) \SAMPLE\blank
\feature[!+][f:smallcapsoldstyle] B) \SAMPLE \blank% \feature[!more][f:noligaturesthinimacron] C) \SAMPLE \blank% \resetandaddfeature[!]addfeature[f:noligaturesupsidedown] D) \SAMPLE \blank
%% Let's revive one of the old featuresets % under development!\feature[+][f:smallcaps] E) \SAMPLE \blank\nextX\addfeature[f:wideimacron] F) \SAMPLE \blank