Getting seperate number from vector?

Let’s say there is a vector which is something like ( x, y, z) and I need only to look up z. So like i can run stuff like if Vectorz > 10 then Hoorah. Is there a vector():z() or something?

[lua]local vector = Vector( 1, 2, 3 );
local x = vector.x;
local y = vector.y;
local z = vector.z;[/lua]

thanks