A function asisgns to each element of a set, exactly one element of a related set.

Ако Π΄Π΅Ρ„ΠΈΠ½ΠΈΡ†ΠΈΠΎΠ½Π½Π°Ρ‚Π° област Π΅ Π΄Π΅ΠΊΠ°Ρ€Ρ‚ΠΎΠ²ΠΎΡ‚ΠΎ ΠΏΡ€ΠΎΠΈΠ·Π²Π΅Π΄Π΅Π½ΠΈΠ΅: