Soluble means able to dissolve, forming a uniform solution in a solvent. Sugar is soluble in water, salt in water, but neither in oil; fat-soluble vitamins dissolve in lipids but not in water. Solubility governs cooking and nutrition alike: soluble fibre dissolves into gut-friendly gels, soluble minerals are the ones the body can absorb, and a drug must be soluble to be absorbed. Temperature, pH, and particle size all shift solubility, which is why hot tea takes more sugar and why vitamin C survives better in acid. The simple word underpins extraction, brewing, brining, and digestion: wherever a solid meets a liquid in food, solubility decides what happens next.