"Alkaline" refers to a substance that has a pH level greater than 7, indicating it is basic rather than acidic. Common alkaline substances include baking soda and lye. Alkaline solutions can neutralize acids, making them useful in various chemical reactions and applications. In nature, many bodies of water, such as lakes and rivers, can be alkaline due to the presence of minerals like calcium carbonate. Alkaline environments can support specific ecosystems and influence the types of organisms that thrive there, such as certain types of fish and plants.