Which term is used to describe a decrease in the number of white blood cells in the blood?

Leukopenia is the term specifically used to describe a decrease in the number of white blood cells (WBCs) in the blood. White blood cells are crucial for the immune system as they help the body fight infections and other diseases. When the count drops below the normal range, it can lead to increased susceptibility to infections, among other health issues.

The other terms listed refer to different medical conditions. Anemia refers to a reduction in red blood cells or hemoglobin, impacting oxygen transport in the body. Thrombocytopenia pertains to a low platelet count, affecting blood clotting. Hemophilia is a genetic disorder that hinders the blood's ability to clot properly due to the lack of certain clotting factors. Each of these conditions affects different components of the blood and serves different clinical significances, making leukopenia the appropriate term for a decrease in white blood cells.