1. Definition:
Atrophy refers to the decrease in the size of a body part, cell, organ, or other tissue while hypertrophy refers to the enlargement of an organ or tissue from the increase in the size of its cells.

2. Cause:
Moreover, atrophy occurs when organs or tissues are not used at all while hypertrophy occurs due to excess work.

3. Results in:
While atrophy results in a decrease in the size of the organ, hypertrophy results in an increase in the size of the organ.

4. Physiological Importance:
Senile atrophy, the atrophy in the thymus after puberty, and atrophy in ovaries and breasts during menopause are the physiological conditions of atrophy while the muscles of bodybuilders and the uterus in pregnant mothers are the physiological conditions of hypertrophy.

5. Pathological Importance
Chronic malnutrition and other chronic diseases cause atrophy, while hypertrophy can be either adaptive or compensatory.

6. Conclusion
Atrophy is the condition of decreasing the size of an organ or tissue when they are not used for a long time. Further, malnutrition, chronic diseases, and aging are the causes of atrophy. On the other hand, hypertrophy is the condition of increasing the size of an organ or tissue due to excess work. Generally, this is by increasing cell volume. As an example, muscle hypertrophy occurs in bodybuilders. Therefore, the main difference between atrophy and hypertrophy is the type of change in organs and tissues and its causes.