Salinity refers to the concentration of dissolved salts in water, typically measured in parts per thousand (ppt). It is an important factor in determining the properties of water bodies, such as oceans, rivers, and lakes. Higher salinity levels are commonly found in oceans, while freshwater sources like rivers and lakes have much lower salinity. Salinity affects the density of water, influencing ocean currents and marine life. Organisms such as fish and plankton have adapted to specific salinity levels, which can impact their distribution and survival. Changes in salinity can result from natural processes or human activities, affecting ecosystems and water quality.