Which of the following best defines a synthesis reaction?

A synthesis reaction, also known as a combination reaction, is characterized by the process where two or more reactants combine to create a new, more complex compound. This type of reaction is fundamental in many areas of chemistry, including organic synthesis and material science.

In a synthesis reaction, the reactants—whether they are elements or simple compounds—undergo a chemical change to form a single product, which reflects the idea of building or constructing a more complex structure from simpler components. The general form can be represented as A + B → AB, where A and B combine to form the product AB.

Understanding this concept is crucial for various applications in chemistry, such as understanding how compounds like water (H2O) are formed from the synthesis of hydrogen (H2) and oxygen (O2) gases. By recognizing that synthesis involves the combination of multiple reactants to yield one product, it helps clarify the nature of this important reaction type.