Solvent
Definition
The substance doing the dissolving: usually the liquid present in the largest amount. Water is called the universal solvent.
Technical definition
The solvent is the dissolving medium of a solution, usually the component present in greatest amount. Water's polarity and hydrogen bonding make it the most common solvent, though organic solvents dominate in many syntheses.
Example
In a sugar-water solution, water is the solvent: it surrounds and separates the sugar molecules.
Common confusion
Like dissolves like. Water dissolves salts and sugars but not oil: matching solvent polarity to solute polarity is the real rule behind the universal solvent nickname.