IPA: /ˈɡlæd.ən/
KK: /ˈɡlæd.ən/
To feel or show happiness or joy.
The news of her promotion gladdened her heart.
Past: gladdened
Past Participle: gladdened
To make someone happy or joyful.
The good news will gladden her heart.
Past: gladdened
Past Participle: gladdened
Gladden is formed from "glad" (from Old English "glæd", meaning joyful or happy) and "-en" (a suffix used to form verbs indicating to make or become). The word "gladden" means to make someone joyful or happy.
Think of the word 'glad' which means happy, and remember that 'gladden' means to make someone happy.