Impair: To impair means to weaken or damage something. For example, if an injury impairs someone's ability to walk properly.
Inhibit: To inhibit means to hinder or restrain something. It can refer to holding back one's thoughts, actions, or emotions due to external factors.
Undermine: To undermine means to weaken or sabotage something indirectly. For instance, spreading rumors about someone in order to undermine their reputation.