An increase in the number of cells in a body part is called hyperplasia.

Here's a breakdown:

* Hyperplasia: This refers to an increase in the number of cells in a tissue or organ due to increased cell division.

* Hypertrophy: This refers to an increase in the size of individual cells, leading to an increase in the size of the tissue or organ.

While both hyperplasia and hypertrophy can result in an enlarged body part, the underlying mechanism is different. Hyperplasia involves more cells, while hypertrophy involves larger cells.