Which term describes the variation in size of red blood cells?

The term that describes the variation in size of red blood cells is anisocytosis. This condition indicates the presence of red blood cells that are significantly different in size compared to one another, which can be a sign of various underlying conditions, such as anemia or nutritional deficiencies.

Macrocytosis refers specifically to the presence of larger than normal red blood cells, while microcytosis describes the presence of smaller than normal red blood cells. Both of these terms indicate a specific type of variation in size rather than the general concept of size variation. Hypochromia pertains to the decreased color intensity of red blood cells, typically due to reduced hemoglobin content, and does not refer to the size of the cells at all. Anisocytosis is a broader term that encompasses all forms of size variation in red blood cells, making it the most appropriate choice for this question.