Update src/networkapi.jl

Co-authored-by: Sam Isaacson <[email protected]>

Author: TorkelE

src/networkapi.jl

@@ -1434,7 +1434,7 @@ integer id of the species within the system.
 - `disablechecks` will disable checking for whether the passed in variable is
   already defined, which is useful when adding many new variables to the system.
   *Do not disable checks* unless you are sure the passed in variable is a new
-  variable, as this will potentially leave the system in an undefined unknown.
+  variable, as this will potentially leave the system in an undefined state.
 """
 function addspecies!(network::ReactionSystem, s::Num; disablechecks = false)
     addspecies!(network, value(s), disablechecks = disablechecks)