Enlighten, v. t.
Etymology: [Pref. en- + lighten: cf. AS. inlihtan. Cf. Enlight.]
1. To supply with light; to illuminate; as, the sun enlightens the earth. His lightnings enlightened the world. Ps. xcvii. 4.
2. To make clear to the intellect or conscience; to shed the light of truth and knowledge upon; to furnish with increase of knowledge; to instruct; as, to enlighten the mind or understanding. The conscience enlightened by the Word and Spirit of God. Trench.
Shades of meaning
Fernald has no entry of its own for enlighten; he lists it under teach.
He lists it without comment; the entries above explain its neighbors.