The citrus fruit among the four species used during Sukkot is the etrog.
An etrog is the fruit of the citron tree, Citrus medica. During Sukkot, it is held together with a lulav, which consists of a palm branch, myrtle branches, and willow branches. Jewish tradition connects these four species with the biblical commandment to rejoice before God during the festival.
An etrog is often chosen for its appearance and the condition of its pitom, the small protruding structure at its blossom end. Some communities use particular varieties or follow detailed rules concerning blemishes and cultivation. The etrog is not simply an ordinary lemon: although both are citrus fruits, an etrog has distinctive botanical and ritual significance. Together, the four species are waved in several directions during prayers, with the exact customs varying by Jewish community.