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:

Example
Description

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.

Example	Description
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.

Classification
The five basic or rather simplest chemical reactions are listed below: [1]

Type
Name (modern chemistry)
Synonyms Name (affinity chemistry)
Formula

1. Combination reaction

A + B → C
2. Decomposition reaction Debonding reaction
Dissolution reaction
A → B + C

3. Substitution reaction
single elective affinity AB + C → AC + B

4. Double substitution reaction
double elective affinity AB + CD → AC + BD
5. Combustion reaction

Fuel + Oxidant → Product + H2O

Type	Name (modern chemistry)	Synonyms	Name (affinity chemistry)	Formula
1.	Combination reaction			A + B → C
2.	Decomposition reaction	Debonding reaction Dissolution reaction		A → B + C
3.	Substitution reaction		single elective affinity	AB + C → AC + B
4.	Double substitution reaction		double elective affinity	AB + CD → AC + BD
5.	Combustion reaction			Fuel + Oxidant → Product + H2O

There are many other varieties of reactions than these five.

See also
● Combination lock theory

References
1. Goldberg, David E. (2003). Beginning Chemistry (combination reaction, pg. 57). McGraw-Hill.

External links
● Combination reaction – Wikipedia.