It has been a two-way process - a process of osmosis where Christianity has over the centuries become an indelible part of Indian plurality. Not only for the urban middle classes enthusiastically getting ready for Christmas, a festival that long ago surpassed the boundaries of mere religion, but also for the many millions who have studied in missionary schools.
Come December and even the smallest local market begins stocking Christmas tree decorations. And most urban Indians may not go to church for Christmas mass or wake up to a white Christmas, but many certainly make sure they are free on Christmas eve to dance and sing 'Dashing through the snow' or 'Silent Night'.
On the flip side, many customs of the majority Hindu religion have assimilated into Christian traditions, making for a uniquely Indian Christianity in a country where the community forms the second largest minority group after the Muslims and constitutes 2.4 percent of its one billion plus population.
'We have incorporated many Hindu traditions into our customs - for example in Christian weddings we have a mangalsutra or the sacred chain worn by married women like those of the Hindus,' said Father Abraham Kakkanattu, director of the Pushpagiri Medical College in Kerala's Thiruvalla town, giving one example.
The influence is undeniable and goes beyond culture.
The Christian community, with a tradition of two millennia, plays a vital role in two important fields in India, primary education and health services.
According to a 2003 report of Directory of Catholic Health Facilities in India, the Catholic church itself has 764 hospitals, 2,975 dispensaries and health centres and 115 medical training centers throughout the country.
There are eight Christian community-run medical colleges apart from 600 Catholic nuns trained as medical doctors serving in rural areas of the country.
The community-run educational institutions claim to have produced many scientific and technological luminaries, besides producing a host of civil servants, entrepreneurs and political leaders, including India's first citizen, President A.P.J. Abdul Kalam.
It's a story that goes way back in time.
Christianity came to India in 52 AD, long before it travelled to many of the west European Christian countries. The religion is believed to have been introduced by St. Thomas, a carpenter by profession and an apostle of Jesus Christ.
Although it reached in the first century, the community confined itself largely to India's southern coastal areas, mainly in Kerala, for almost 1,500 years. It spread to other parts like Goa and the northeast, particularly Mizoram - now a Christian majority state - after the arrival of the Portuguese in India in the 15th century, followed by the French and the British.
'It is absolutely wrong to confuse Indian Christianity with colonial rule. When St. Thomas came here there was no colonialism,' Kakkanattu told IANS.
'In fact, missionary activity, which was already there when the Portuguese and the British came, helped in mobilising general opinion against foreign rule,' said Kakkanattu, the priest from the southern state that has a heavy Christian population.
Sociologists are in fact of the view that Christians in India represented active de-colonisation as well.
'I think the religion represents de-colonisation also. Personalities like Mother Teresa proved that it was no longer the religion of oppressors or conquerors,' said Ananth Pathak, a sociologist at Jawaharlal Nehru University.
It is believed that the modern Indian renaissance began from West Bengal largely under the influence of Christianity, which brought in a new philosophy and social ideology.
Many prominent opinion makers, social leaders and outstanding educationists of Kolkata, the seat of the British empire in the last century, were Bengali Christians, like W.C Bonnerjee, the first president of the Indian National Congress, and Michael Madhusudhan Dutt, poet and playwright.
Many Christian scholars made significant contributions to the development of languages in India. Belgian priest Camil Bulke's English-Hindi dictionary, for instance, is still the first reference for any translation needed. And German missionary Herman Gündert is still appreciated for his foresight in bringing out the first Malayalam-English dictionary.
The Catholic Church in India comprises three individual Churches - Latin, Malabar and Malankara. Among the other Christian groups are Syrian Christians, Knanaya, Goan Christians, Tamil Christians and Naga Christians, with each category having its own distinct language and social customs.
But they are still all one, in sync, despite all differences, with one another and the pan-Indian identity to which all belong.