To enlighten someone means to explain something clearly to him. If your friend is behaving strangely but insists she has a reason for it, you could ask her to enlighten you.

Enlighten comes from the metaphor that ignorance is a state of being "in the dark," and that knowledge is illuminating. We use enlighten as a verb meaning to clear up, to remove confusion. Light is also a powerful metaphor for spiritual insight. If you have a great revelation about the divinity of the world, you could say you have been enlightened. The era known as the "Age of Reason" is also called the Enlightenment.

Definitions of enlighten

v give spiritual insight to; in religion

Type of:
prophesy, vaticinate
predict or reveal through, or as if through, divine inspiration

v make understand

“Can you enlighten me--I don't understand this proposal”
Type of:
instruct, learn, teach
impart skills or knowledge to

v make free from confusion or ambiguity; make clear

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