why is thomas in the bible called the twin
Thomas the Apostle The name Thomas (Koine Greek: Θωμᾶς) given for the apostle in the New Testament is derived from the Aramaic or Classical Syriac: ܬܐܘܡܐ‎ Toma, equivalently from Hebrew Teom, meaning "twin". The equivalent term for twin in Greek, which is also used in the New Testament, is Δίδυμος Didymos.
Trinity The Christian doctrine of the Trinity (Latin: Trinitas, lit. 'triad', from trinus, "threefold")[2] holds that God is three consubstantial persons[3] or hypostases[4]—the Father, the Son (Jesus Christ), and the Holy Spirit—as "one God in three Divine Persons". The three persons are distinct, yet are one "substance, essence or nature" (homoousios).[5] In this context, a "nature" is what one is, whereas a "person" is who one is.[6][7][8] The opposing view is referred to as Nontrinitarianism.