There are 2 main definitions of lighten in English:

lighten1

Line breaks: light¦en
Pronunciation: /ˈlʌɪt(ə)n
 
/

verb

1Make or become lighter in weight, pressure, or severity: [with object]: efforts to lighten the burden of regulation [no object]: the strain had lightened
More example sentences
  • When they had eaten enough, they lightened the ship, throwing out the wheat into the sea.
  • The menu has been conceived along American or lightened Continental lines, and despite an occasional, surprising flaw, the food is generally well prepared.
  • To make matters worse, Ellen wasn't lightening the homework load one bit.
Synonyms
make lighter, lessen, reduce, decrease, diminish, moderate, soften, ease, temper;
1.1Make or become more cheerful or less serious: [with object]: she attempted a joke to lighten the atmosphere [no object]: try to lighten up and think positive
More example sentences
  • But Dad, he seriously needs to lighten up, maybe get a girlfriend or something.
  • As usual, there was a large group of rowdy sailors surrounding the table, which actually helped to lighten up the heavy atmosphere.
  • I guess they were trying to lighten up the atmosphere… or something like that.
Synonyms
cheer (up), brighten, gladden, hearten, perk up, lift, ginger up, enliven, boost, buoy (up), elate, inspire, uplift, sweeten, revive, restore, revitalize, stimulate;
enhance, improve, leaven
informal jazz up
rare inspirit

Definition of lighten in:

There are 2 main definitions of lighten in English:

lighten2

Line breaks: light¦en
Pronunciation: /ˈlʌɪt(ə)n
 
/

verb

1Make or become lighter or brighter: [no object]: the sky began to lighten in the east [with object]: she had lightened her hair
More example sentences
  • As the sky began to lighten in the east, humans and lizards moved quickly through the trees, wearing earthen colors and staying as low as possible to the ground.
  • The sky was beginning to lighten in the east, which meant they were running out of time.
  • I could watch the last star fade as the sky lightened and birds began to chatter amongst themselves about the coming day.
Synonyms
become lighter, grow brighter, brighten
make lighter, make brighter, brighten, light up, illuminate, throw/cast/shed light on, shine on, irradiate, flood with light, floodlight
literary illumine
whiten, make white(r), bleach, peroxide, blanch, make pale(r), remove colour from, fade, wash out, decolour, decolorize
1.1 [with object] archaic Enlighten spiritually: now the Lord lighten thee, thou art a great fool
2 [no object] (it lightens, it is lightening, etc.) rare Flash with lightning: it thundered and lightened
Synonyms
emit lightning, flash lightning
rare fulgurate

Definition of lighten in: