The diya (from Sanskrit dipa, "lamp") is the quintessential lamp of Hindu worship — a small clay bowl filled with ghee or sesame oil and a cotton wick, lit before deities during puja and aarti. Lighting a diya symbolizes the victory of light over darkness and knowledge over ignorance, the central theme of Deepavali (Diwali), "the row of lamps," when homes are lined with dozens of diyas to welcome Lakshmi. Many households light a diya morning and evening at the home altar and under the tulsi plant. Ghee lamps are considered the most sattvic (pure); the direction the wick faces and the number of wicks carry traditional significance in some communities.