"to make less heavy, to lighten a load," mid-14c., lighten, lightnen, from light (adj.1) + -en (1). Figuratively "to make cheerful" from c. 1400. Intransitive sense "become less heavy" is from 1720. Related: Lightened; lightening.
lighten (v.2)
"shed light upon, illuminate, make light or bright," early 14c., from light (n.) + -en (1). Intransitive meaning "to become brighter" is late 14c.; of faces, expressions, etc., from 1795. Meaning "to flash lightning" is from mid-15c. Related: Lightened; lightening.
the conversation lightened me up a bit
she lightened the load on the tired donkey
after a glass of wine, he lightened up a bit
The room lightened up
lighten the burden of caring for her elderly parents
ligation
ligature
liger
light
light bulb
lighten
lightening
lighter
light-fingered
lightfoot
light-headed