The traditional oil lamp used in Diwali is called a diya.
A diya is usually a small lamp made from fired clay, with a cotton wick dipped in vegetable oil or ghee. Diyas can also be made from brass, silver, leaves, stone, or other materials, and larger ornamental versions may hold several wicks. Their design is simple, but their ritual meaning is substantial.
During Diwali, people light diyas in homes, temples, courtyards, and near entrances. The flame is commonly understood to symbolize light overcoming darkness, good overcoming evil, and knowledge overcoming ignorance. Many Hindu traditions associate Diwali with Rama’s return to Ayodhya after exile and victory over Ravana; other regional traditions emphasize Lakshmi, Kali, or different religious events. Jains and Sikhs also observe related festivals and lighting practices.
Diya is not simply another word for every decorative light used during Diwali. Candles, electric lamps, string lights, and lanterns are also common, but the small oil- or ghee-burning lamp is specifically the diya. The festival’s name, Deepavali, is commonly explained as meaning a row or series of lights.