The IPA symbol for the voiced postalveolar fricative, as in “genre,” is ʒ.
The symbol ʒ is called ezh and represents a voiced sibilant made with the tongue near the area just behind the alveolar ridge. “Voiced” means the vocal folds vibrate during the sound, while “fricative” means air passes through a narrow constriction to create audible friction. In English, the sound occurs in words such as “measure,” “vision” and “genre,” often because of French influence or historical sound changes.
This consonant is easy to confuse with the voiceless postalveolar fricative ʃ, the “sh” sound in “ship.” It is also distinct from dʒ, the voiced postalveolar affricate heard at the start of “judge”: dʒ begins with a stop closure before the fricative release, whereas ʒ is a continuous fricative. The letter z is not the correct IPA symbol here; z normally represents a voiced alveolar fricative, as in the sound at the end of “buzz.”