What is an example of an additional reaction?

Hint: First try to understand the addition reaction and how it takes place and then further we can easily give its example. As we know that an additional reaction is a chemical reaction in organic chemistry wherein two or more reactants come together to form a larger single product.

Complete answer:
Let us first understand about chemical reactions followed by the addition reaction and its examples as follows:-
-In chemistry, when any 2 or more compounds or molecules with different or similar properties react with each other under the influence of external conditions like temperature, pressure and reagents to form a new compound with different properties is called a chemical reaction.
-The additional reaction can be described as the reaction where two compounds combine to form a new compound without any loss of atoms. In this reaction a pi bond which is a weaker bond is converted into two strong sigma bonds. The electrophilic reaction can be categorized further into two types which are electrophilic addition reaction and nucleophilic addition reaction.
-The additional reaction is generally shown by unsaturated hydrocarbons which contain either double or triple bonds and it is used to convert unsaturated compounds into saturated compounds.
-The example of addition reaction is as follows:-
$C{{H}_{2}}=C{{H}_{2}}+{{H}_{2}}O\to C{{H}_{3}}C{{H}_{2}}OH$
This is the hydration reaction in which ethene (unsaturated compound) reacts with water to form ethanol (saturated compound).

Note:
-Remember that addition reaction is kind of a reverse decomposition reaction as decomposition reaction is a reaction where one compound breaks into one or more elements or compounds.
-In addition reaction, both electrophile and nucleophile groups play a major role.