First principles (9)

I believe the answer is:
rudiments
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">first principles</span>' is the definition.<br/ ><span class="explanation-format__explanation">('rudiment' can be a synonym of 'first principle')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for rudiments that I've seen before include "basic principles" , "Basics of any subject" .)