Hinduism might be a religion for most of us but I feel that Hinduism is a way of life. We call it the Hindu Dharma. Dharma and religion are not the same and should not be confused. Religion is a subset of Dharma. Hinduism is also known as the Sanaatan Dharma.
A religion is founded by someone. One belongs to the same religion if one shares a common symbol, common religious texts, common God and a common founder. Most of the times, it is the religious movement that gives birth to a religion. Thus, a religion has a date of origin. We can also say that a religion has a group of people who think and believe alike.
Dharma on the other hand originates from the Sanskrit root dhri, which means “that which maintains the stability and harmony of the universe.” Dharma describes the behavior of things, duty, law, ethics, virtue, etc. Every entity in the universe has its dharma or duty or has to abide by certain laws―the electron has the dharma to move in a certain manner and clouds have their own Dharma or duty and similarly a man. In modern term of Dharma is Physics.