Enlightenment broadly means wisdom or understanding enabling clarity of perception. However, the English word covers two concepts which can be quite distinct: religious or spiritual enlightenment and secular or intellectual enlightenment. This can cause confusion, since those who claim intellectual enlightenment often reject spiritual concepts altogether.

In religious use, enlightenment is most closely associated with South and East Asian religious experience, being used to translate words such as (in Buddhism) nirvana, bodhi or satori, or (in Hinduism) moksha. The concept also has parallels in the Abrahamic religions (in the Kabbalah tradition in Judaism, in Christian mysticism or Gnosticism, and in the Sufi fitra tradition of Islam).

In secular use, the concept refers mainly to the European intellectual movement known as the Age of Enlightenment, also called the Age of Reason referring to philosophical developments related to scientific rationality in the 17th and 18th centuries.