olemus
vektorruumi vektorite aditiivse rühma ühikelement
= a vector which is of zero length and all of whose components are zero
http://mathworld.wolfram.com/ZeroVector.html

ülevaateid
https://mathinsight.org/zero_vector
https://www.maths.usyd.edu.au/u/geoffp/lm-ss/lectp4.pdf
http://cs.brown.edu/courses/csci0530/current/slides/09-13-2017.pdf