Explanation:
A reaction in which two reactants combine together to form a new compound is known as synthesis reaction.
A reaction in which reactants give products and the products in turn form the reactants is known as reversible reaction.
When a compound breaks into atoms or its constituent parts then it is known as decomposition reaction.
When there is trade of ions or constituent parts by the substrate then this is known as exchange reaction.
Therefore, the given terms and definitions are matched as follows.
1. Two or more units are added together to form a new compound - Synthesis reaction.
2. Reactants used to form products can also be obtained from those products - Reversible reaction.
3. A compound is broken into its constituent parts - Decomposition reaction.
4. The substrates trade constituent parts - Exchange reaction.
