Define sexual dimorphism.

Explanation

### Step-by-Step Solution:

1. **Definition of Sexual Dimorphism**: Sexual dimorphism refers to the differences in physical characteristics between male and female individuals of the same species.

2. **Physiological Differences**: These differences can be seen in physiology, which includes functions and processes within the body. For example, in humans, females experience a menstrual cycle, while males do not.

3. **Morphological Differences**: Sexual dimorphism also includes morphological differences, which pertain to the form and structure of organisms. For instance, in roundworms, female roundworms are typically longer than male roundworms.

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