IPA: /ˈrɛd.ən/
KK: /ˈrɛdən/
To change color to red or to become red in appearance.
When she heard the compliment, her cheeks began to redden.
Past: reddened
Past Participle: reddened
To cause something to become red in color.
The artist decided to redden the sky in her painting to create a dramatic effect.
Past: reddened
Past Participle: reddened
Reddens is formed from "red" (from Old English "read", meaning the color red) and "-en" (a suffix used to form verbs indicating to cause to become). The word "redden" means to cause something to become red or to turn red.
Think of the color 'red' and remember that 'redden' means to make something turn red.