What is a condensation or dehydration synthesis reaction?

A dehydration synthesis reaction is the combination of elements and/or simple compounds to form a complex compound by removing the H2O.

Dehydration synthesis occurs in the combination of many things, such as two monosaccharides that come together to form a disaccharide. To form the disaccharide, the OH of one molecule (such as glucose) bonds to the H in the other OH molecule (such as glucose, fructose, or galactose). This forms a H2O molecule (water), and then the excess O forms a bridge between the two monosachrides; forming a disacaride.