Which of the following refers to an abnormal increase in the number of cells?

The term that refers to an abnormal increase in the number of cells is hyperplasia. This process typically results from an increase in cell division and can occur in response to various stimuli such as hormonal signals or chronic irritation. Hyperplasia is generally a controlled process and can lead to tissue enlargement, but it does not always indicate a malignant process.

Hypertrophy, in contrast, refers to an increase in the size of existing cells rather than an increase in cell number. Dysplasia involves abnormal changes in the size, shape, and organization of cells, which may indicate pre-cancerous conditions but does not specifically address the increase in cell quantity. Carcinoma refers to a type of cancer that arises from epithelial cells, characterized by uncontrolled cell proliferation, and is more associated with malignancy rather than simply the increase in cell numbers seen in hyperplasia.