Adityas in Hinduism means Surya (Sun God) for many. But this is not so. The sons of Sage Kashyapa and Aditi are known as Adityas. The word Adityas means ‘whose mother is Aditi.’ Usually there are twelve Adityas. But some scriptures give the number as Seven and some give the number as Eight.
Twelve Adityas
Dhata, Mitra, Aryama, Rudra, Varuna, Surya, Bhaga, Vivasvan, Pusha, Savita, Tvasta and Vishnu.
Valmiki Ramayana (Aranya Kanda) and Mahabharata (Adi Parva) state that besides the twelve sons Aditi had 21 children. Thus Aditi had 33 children (12 + 21). From the 33 sons of Aditi were born the thirty three crore devatas. Of these the eldest is Indra and youngest is Vamana.
Scholars are of the view that there are many different Adityas in Rig Veda. The most important Aditya in the Rig Veda is Varuna. Many Adityas were merged with Surya or Indra or Shiva.
Adityas in Bhagavad Gita
Adityas is mentioned in the Bhagavad Gita, especially while describing the cosmic form of Bhagavan Vishnu.
Among the (twelve) Adityas I am Vishnu; (10.21)
Behold the Adityas, the Vasus, the Rudras, the (two) Ashwins and also the Maruts; behold many wonders never seen before, O Bharata. (11.6)
The Rudras, Adityas, Vasus, Sadhyas, Vishwa-devas, the two Ashwins, Maruts, Ushmapas and hosts of Gandharvas, Yakshas, Asuras and Siddhas – they are all looking at you, all quite astonished. (11.22)