To synthesise is to make or build something by combining simpler parts — whether molecules, materials, or ideas. A chemist synthesises a flavour compound by linking precursor molecules through controlled reactions; a cell synthesises proteins by joining amino acids according to genetic instructions; a researcher synthesises findings by weaving separate studies into a single coherent conclusion. In industry, synthesis is how vitamins, sweeteners, preservatives, and pharmaceuticals are manufactured at scale, often more cheaply and purely than extraction from natural sources. The skill lies in planning the sequence: each step must work in high yield, or the losses multiply across the chain. It is construction at the molecular or intellectual level.