Introduction:
The Human Development Index (HDI) is a composite measure of human development, which takes into account various indicators to assess the well-being of individuals in a country. These indicators include life expectancy, education, and per capita income. However, social inequality is not used as an indicator in calculating the HDI.

Explanation:
1. Life Expectancy: Life expectancy at birth is one of the indicators used in calculating the HDI. It measures the average number of years a newborn is expected to live, and it reflects the overall health and well-being of individuals in a country.

2. Education: Education is another important indicator used in calculating the HDI. It takes into account two components: mean years of schooling and expected years of schooling. Mean years of schooling measures the average number of years of education received by individuals aged 25 and older, while expected years of schooling measures the number of years of education that a child of school entrance age can expect to receive in the future.

3. Per Capita Income: Per capita income is also considered in calculating the HDI. It represents the average income per person in a country and is a measure of the economic well-being of individuals. Higher per capita income indicates greater access to resources and opportunities for individuals to improve their living standards.

4. Social Inequality: While social inequality is an important issue in measuring development and well-being, it is not directly included as an indicator in the calculation of the HDI. The HDI focuses on average achievements in life expectancy, education, and income, rather than on the distribution of these achievements within a country. However, it is worth noting that social inequality can have an impact on the overall well-being of individuals and can influence the effectiveness of policies and programs aimed at improving human development.

Conclusion:
In conclusion, the Human Development Index (HDI) is a composite measure that takes into account indicators such as life expectancy, education, and per capita income to assess human development. Social inequality, although an important consideration in measuring well-being, is not directly included as an indicator in the calculation of the HDI.