Calcification refers to the process by which calcium deposits form in tissues or organs. This can occur naturally as a part of normal development, such as the hardening of bones during growth, or it can be abnormal and result from various conditions such as arthritis or kidney stones. In medical terms, calcification is often associated with the buildup of calcium phosphate in soft tissues like blood vessels, heart valves, or other organs, which can lead to a narrowing or blockage of those structures and cause various health problems.