Final answer:
Hyperplasia is an increase in cell number, hypertrophy is an increase in cell size, atrophy is a decrease in cell size or number, and neoplasia is the abnormal growth of cells which can be benign or malignant.
Step-by-step explanation:
Hyperplasia refers to an increase in the number of cells in a tissue or organ, resulting in its enlargement. This can be seen, for example, when the uterus increases in size during puberty. Hypertrophy refers to an increase in the size of existing cells in a tissue or organ, often as a result of exercise. On the other hand, atrophy refers to the shrinkage or wasting away of a tissue or organ due to a decrease in cell size or number.
Neoplasia refers to the abnormal and uncontrolled growth of cells, which can form tumors. These tumors can be classified as benign or malignant, with malignant tumors being cancerous and capable of invading surrounding tissues and forming metastases.