Sets of points, in math (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
loci
'sets of points in math' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for loci that I've seen before include "Particular positions" , "Particular places" , "locations" , "Points where something occurs; coil (anag.)" , "sites" .)