Vedelikku

Vedelikku is the Estonian term for liquid in the partitive case. In everyday language it refers to any fluid substance; in scientific usage it denotes one of the fundamental states of matter. A liquid has a definite volume but no fixed shape, conforming to and flowing within its container.

Liquids are generally incompressible at ordinary pressures and temperatures, though they can be compressed slightly. They display cohesive forces that give rise to surface tension and adhesive forces that enable wetting of surfaces. Key properties used to describe liquids include density (mass per volume), viscosity (resistance to flow), surface tension, and vapor pressure. Temperature and pressure influence these properties and drive phase changes such as evaporation and boiling.

Liquids can be classified by composition (pure liquids such as water, ethanol, or mercury; mixtures such as saline solutions or oils), by miscibility (miscible or immiscible pairs), and by phase behavior (single-liquid systems versus multi-component suspensions). Phase diagrams illustrate how temperature and pressure determine states of matter and transitions between them. Common phenomena include capillary action, diffusion within liquids, and the formation of interfaces with other phases.

Examples include water, alcohols, glycerol, saline solutions, and vegetable oils. In science and industry, liquids serve as solvents, heat transfer media, reactants, lubricants, and cleaning agents. Properties such as density, viscosity, and surface tension are routinely measured for quality control, process design, and fundamental research.

Etymology: vedelikku is the partitive form of vedelik, the Estonian word for liquid.