Lighten, v. t.
Etymology: [See Light not heavy.]
1. To make lighter, or less heavy; to reduce in weight; to relieve of part of a load or burden; as, to lighten a ship by unloading; to lighten a load or burden.
2. To make less burdensome or afflictive; to alleviate; as, to lighten the cares of life or the burden of grief.
3. To cheer; to exhilarate. Lighens my humor with his merry jests. Shak.
3 other Webster entries under this spelling
Lighten, v. i.
To descend; to light. O Lord, let thy mercy lighten upon us. Book of Common Prayer [Eng. Ed.]
Lighten, v. i. [imp. & p. p. Lightened; p. pr. & vb. n. Lightening.]
1. To burst forth or dart, as lightning; to shine with, or like, lightning; to display a flash or flashes of lightning; to flash. This dreadful night, That thunders, lightens, opens graves, and roars As doth the lion. Shak.
2. To grow lighter; to become less dark or lowering; to brighten; to clear, as the sky.
Lighten, v. t.
1. To make light or clear; to light; to illuminate; as, to lighten an apartment with lamps or gas; to lighten the streets. [In this sense less common than light.] A key of fire ran all along the shore, And lightened all the river with a blaze. Dryden.
2. To illuminate with knowledge; to enlighten. [In this sense less common than enlighten.] Lighten my spirit with one clear heavenly ray. Sir J. Davies.
3. To emit or disclose in, or as in, lightning; to flash out, like lightning. His eye . . . lightens forth Controlling majesty. Shak.
4. To free from trouble and fill with joy. They looked unto him, were lightened. Ps. xxxiv. 5.
Shades of meaning
Fernald has no entry of its own for lighten; he lists it under alleviate.
Where he writes about it:
Etymologically, to alleviate is to lift a burden toward oneself, and so lighten it for the bearer; to relieve is to lift it back from the bearer, nearly or quite away; to remove is to take it away altogether. — from alleviate
We abate a fever; lessen anxiety; moderate passions or desires; lighten burdens; mitigate or alleviate pain; reduce inflammation; soften, assuage, or moderate grief; we lighten or mitigate punishments; we relieve any suffering of body or mind that admits of help, comfort, or remedy. — from alleviate