Thomas was one of the 12 apostles of Jesus Christ. In the Synoptic gospels and the Book of Acts he is listed with the other apostles, but nothing else is written about him.
However, we are provided with far more information in the Gospel of John where Thomas appears in several scenes, the best known being where doubts the resurrection and demanded to feel Jesus' wounds before being convinced (20:24-9) - from which comes the term Doubting Thomas. In three of these passages (11:16; 20:24; and 21:2), Thomas is identified as "Thomas, also called the Twin (Didymus)". The name Thomas comes from the Aramaic word for twin. Syrian tradition, apparently aware of the awkwardness of the name "Thomas the Twin", states that his full name as Judas Thomas, or Jude Thomas, and as early as the Acts of Thomas (written in east Syria in the early 3rd century) he was identified with Jude, one of the brothers of Jesus Christ (Mark 6:3), and thus said to be the twin brother of Jesus.
Thomas is revered as a saint in both the Roman Catholic Church and in the Eastern Orthodox Church, and is remembered each year on St Thomas Sunday, which is always one week after Easter.
Thomas is also part of the legend of king Abgar of Edessa, for having sent Thaddaeus to preach in Edessa after the Ascension (Eusebius, HE 1.13; III.1; Ephraem also recounts this legend.)
The Portuguese encountered Christians in 1498 while exploring the Malabar coast, who traced their foundations to Thomas. However, they did not accept the legitimacy of local Malabar traditions, and they began to impose Roman Catholic practices upon the Saint Thomas Christians, some of whom conformed to become the Syro-Malabar Catholic Church; others revolted and organized themselves to become the Indian Orthodox Church; and a number have since joined other Christian denominations.
No written records of the apostle's voyage to India exist. Modern scholars doubt that Thomas did reach India; KS Latourette, in A History of the Expansion of Christianity does not allow the possibility of Christians coming to India by any route before the third century AD. He states that Christianity was brought to India in AD 345 by Syrian Christians fleeing persecution, led by the merchant Thomas of Cana.
The best known of these documents is the Gospel of Thomas, an apocryphal work. The introduction claims it is the work of "Didymos Judas Thomas" - who has been identified with Thomas. This work was discovered in a Coptic translation in 1948 at the Egyptian village of Nag Hammadi, near the site of the monastery of Chenoboskion. Once the Coptic text was published, scholars recognized that an earlier Greek translation had been published from fragments of papyrus in the 1890s. No Christian denomination has recognized this work as part of the Bible.