darken

verbs

become dark or darker
"The sky darkened"
darken
is derived from
darkening
antonym
lighten
is a type of (narrower)
undergo a change; become different in essence; losing one's or its original nature
"She changed completely as she grew older"; "The weather changed last night"
change
tarnish or stain
"a scandal that darkened the family's good name"
darken
is a type of (narrower)
make dirty or spotty, as by exposure to air; also used metaphorically
"The silver was tarnished by the long exposure to the air"; "Her reputation was sullied after the affair with a married man"
defile, maculate, stain, sully, tarnish
make dark or darker
"darken a room"
darken
is derived from
darkening
antonym
brighten
is a type of (narrower)
cause to change; make different; cause a transformation
"The advent of the automobile may have altered the growth pattern of the city"; "The discussion has changed my thinking about the issue"
alter, change, modify
causes
become dark or darker
"The sky darkened"
darken