A chemical reaction where aminos, carbohydrates, and lipids combine into polymer chains. As an example:

Your standard amino acid has two main functional groups:

• An amino group (NH₂).
• A carboxyl group (COOH).

When two amino acids attach to each other, the resulting linkage causes an (OH) to detach from the carboxyl group, and an (H) to attach from the amino group. When these two are combined, they form (H₂O), also known as water.
Therefore, the process is called dehydration synthesis, because:

• Water is removed from the compound, thus 'dehydration.'
• A compound is formed, or synthesized.

The reverse/inverse of dehydration synthesis is hydrolysis.