Definition of a Hindu
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Aa sindho: sinduparyantham
yasya bhaaratha bhoomikaa
maathru bhoo: pithru bhoo (punya)
schaiva sa vai Hindu iti smruthaa:

Whomsoever, is considering the land between the sapta sindu (Indus Valley River) up to Indian Ocean as the motherland, fatherland and holy land, is known as Hindu.

Hindustanam which is defined as follows
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Himaalayam samaarabhya
yaavath hindu sarovaram
tham deva nirmitham desam
hindustaanam prachakshate.

The land created by god himself; lying between Himalayas and Indian Ocean is known as Hindustanam

Unlike other religions, Hindu dharma has many specialties. This is not known as a religion, it is known as the dharma; Sanaathana Dharma. Sanaathana means according to Bhagavath Geetha, which cannot be destroyed by fire, weapons, water, air, and which is present in all living and non living being. Dharma means, the way of life which is the ‘total of all aachaaraas or customs and rituals’. The aachaaraas which are to be performed by the mother is known as maathru dharma that of father is known as pithru dharma. Similarly there are puthra dharma (dharma of son), aachaarya dharma (dharma of teacher), as a continuation we can say bhraathru (brother) dharma, bhagini (sister) dharma, poura (citizen) dharma, raja (king) dharma and so on. All these dharmas have been described in detail giving the specific importance in the dharma saasthra and smruthies. There is no specific English word for dharma, but it is the sum of the duties + responsibilities + privileges of that individual.

What is the Sanaathana dharma?
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It is the total of maathru dharma + pithru dharma + puthra dharma + puthree dharma + aachaarya dharma + poura dharma + …+…etc. Hence we say Hinduism is not a religion but the way of life.

Sanaathana Dharma has its foundation on scientific spirituality. Ancient rishies are the authors of the Vedas, Puranaas, Itihaasaas and Smruthies which are known as Hindu religious or spiritual books. Those rishies themselves wrote the books on Economics - Artha saastra, Music and dance - Gaandharva Veda, Science of heath and food - Ayurveda, Civil engineering and sculpture Sthaapathya veda etc. These are well known scientific books. In the entire ancient Hindu literature one can see that science and spirituality are integrated. It is mentioned in the 40th chapter of the Yajurveda known as Eesaavaasya Upanishad that use the scientific knowledge for solving the problems in our life and use the spiritual knowledge for attaining immortality through philosophical outlook.

Avidyayaa mruthyum theerthwaa
vidyayaa amruthamasnuthe