A face-threatening act is an utterance or action that challenges the self-esteem or social identity of an individual within a conversation. This concept is crucial for understanding how people communicate and navigate social interactions, particularly when it comes to maintaining politeness and avoiding conflict. It plays a significant role in speech acts, where the intention behind a statement can either reinforce or undermine someone's face, as well as in face theory, which emphasizes the importance of preserving the 'face' or social persona of individuals during communication.