For
[[전사,surjection]] [[전사함수,surjective_function]]
'''단사,injection''' [[단사함수,injective_function]]
[[전단사,bijection]] [[전단사함수,bijective_function]]

'''injective''' adj.

curr. see: [[함수,function#s-5]] and/or [[사상,map]]

chk: [[일대일,one-to-one]] = injective 완벽히 같은 거 맞는지?
 https://mathworld.wolfram.com/One-to-One.html

sub?
[[단사함수,injective_function]] = [[일대일함수,one-to-one_function]] - curr at [[함수,function#s-5.1]]
단사조각? [[injective_patch]] — [[조각,patch]] ([[미분기하학,differential_geometry]])

tbw: [[판정법,test]] > horizontal line test 와의 밀접한 관련성?? chk - 을 적을 것

chk, tmp from https://blog.naver.com/hafs_snu/221085743625
{
단사함수의 정의
각각의 $y\in Y$ 에 대해 $f(x)=y$ 를 만족하는 $x\in X$ 가 최대 한 개 뿐이다. (0개 또는 1개)
$\forall x_1 \forall x_2 (f(x_1)=f(x_2)) \to (x_1=x_2)$
}

https://planetmath.org/injectivefunction
https://encyclopediaofmath.org/wiki/Injection
http://foldoc.org/injection
https://artofproblemsolving.com/wiki/index.php/Injection
https://ncatlab.org/nlab/show/injection

tmp
 https://everything2.com/title/injection
 https://everything2.com/title/injective
 https://en.citizendium.org/wiki/Injective_function