olemus
(1) matemaatikas: (in math):
algebralises muutkonnas defineeritud
n-muutujaline funktsioon, mis iga punkti ümbruses
käitub nagu ratsionaalfunktsioon (st polünoomide jagatis)
= an n-variable function defined in algebraic variety that behaves like a rational function (i.e. like a quotient of two polynomials) around each point

https://encyclopediaofmath.org/wiki/Regular_function

https://en.wikipedia.org/wiki/Morphism_of_algebraic_varieties

(2) JavaScriptis (in JavaScript):
http://images.slideplayer.com/29/9456463/slides/slide_3.jpg

https://dmitripavlutin.com/differences-between-arrow-and-regular-functions/

https://dmitripavlutin.com/6-ways-to-declare-javascript-functions/