Chinese words with 忧 character meaning (HSK)

后顾之忧

HOU4, GU4, ZHI1, YOU1
fears of trouble in the rear (idiom), family worries (obstructing freedom of action), worries about the future consequences, often in negative expressions, meaning 'no worries about anything'

无忧无虑

WU2, YOU1, WU2, LV4
carefree and without worries (idiom)

忧郁

YOU1, YU4
sullen, depressed, melancholy, dejected