In chemistry, a combination reaction is a chemical reaction in which two or more reactants combine or bond to form a new single product. The generic combination reaction, in which two reactants, A and B, combine to form a single product C, is typically written as:
|A + B → C||The atomic compositions of the reactants, A and B, are modified.|
|A + B → AB||The reactants, A and B, retain their atomic geometry.|
|A + B + C → ABC||Three reactants, A, B, and C, combined into a singe unit, while retaining their internal atomic geometry.|
In the older eighteenth century affinity reaction nomenclature this reaction likely has a name, similar to a single elective affinity reaction, but the name needs to be tracked down.
The five basic or rather simplest chemical reactions are listed below: 
There are many other varieties of reactions than these five.
● Combination lock theory
1. Goldberg, David E. (2003). Beginning Chemistry (combination reaction, pg. 57). McGraw-Hill.
● Combination reaction – Wikipedia.