olemus
(1a) topoloogias
pinna "avade" arv pinna karakteristikuna
= the number of "holes" of a surface
http://ned.ipac.caltech.edu/level5/March01/Carroll3/Figures/fig_two2.jpg

https://image.slidesharecdn.com/topology-111123232009-phpapp02/95/topology-51-728.jpg

https://en.wikipedia.org/wiki/Genus_(mathematics)

http://planetmath.org/genusoftopologicalsurface

http://www.ams.org/notices/200906/rtx090600713p.pdf

(1b) graafiteoorias
vähim naturaalarv n, mille korral
graafi saab lõikumisteta esitada n avaga pinnal
= the minimal integer n such that the graph can be drawn without crossing itself on a sphere with n handles
https://mathworld.wolfram.com/GraphGenus.html
https://en.wikipedia.org/wiki/Graph_embedding

vt ka
- sugu (1)
- sugu (2)