hū
suddenly
Phonosemantic compound. 心 represents the meaning and 勿 represents the sound.
Evolution

Bronze script
Late Warring States (~250 BC)
Seal script
Shuowen (~100 AD)
Clerical script
Eastern Han dynasty (25-220 AD)Regular script
ModernDefinitions
Component uses
Meaning component in 1 character (0 verified)
Sources