Math measurements (5)
I believe the answer is:
radii
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">math measurements</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for radii that I've seen before include "Half-diameters" , "Veins of insect's wings" , "Lines from a circle's centre to the circumference" , "Spokes of wheel - bones of arm" , "Lines from the centre to the circumference of a circle" .)