Condensation reactions are chemical processes where two molecules combine to form a larger molecule, releasing a small molecule, often water. This type of reaction is common in organic chemistry and is essential for forming complex structures like proteins and polysaccharides. In a condensation reaction, functional groups from the reacting molecules interact, leading to the formation of a covalent bond. The released small molecule, typically H2O, is a byproduct of the reaction. These reactions are crucial in biological systems, as they help build macromolecules necessary for life.