What describes an abnormal increase in the number of white blood cells?

Leukocytosis refers specifically to an abnormal increase in the number of white blood cells (leukocytes) in the blood. This condition often occurs in response to various factors such as infection, inflammation, stress, or other medical conditions. White blood cells are crucial components of the immune system, and their increased presence is typically a sign that the body is fighting off illness or responding to other stimuli.

In contrast, polycythemia refers to an increase in red blood cells, thrombocytosis is characterized by an elevated number of platelets, and leukopenia indicates a decrease in white blood cells. Understanding these definitions clarifies why leukocytosis is the accurate term for describing an increase in white blood cell count.