1) Subjoining 2) Subjunction 
• (n.) The act of supplementing.
Adding nutrients to the diet.
The release and management of artificially propagated fish in streams with the intent to increase or establish wild fish populations while minimizing associated genetic and ecological risks.
Sup`ple·men·ta'tion noun The act of supplementing. C. Kingsley. 
[n] - the act of supplementing
subjunction noun the act of supplementing
the act or process of supplementing. · the state of being supplemented. · something that supplements.