过失 (guò shī) is a formal noun meaning 'fault, mistake' and is the standard legal term for negligence or culpable error. Compared to 错误 (cuò wù, general mistake/wrongness), 过失 always implies a degree of responsibility or omission, and it's more serious than 失误 (shī wù, a performance slip). Unlike 过错 (guò cuò, personal blame) and 疏忽 (shū hu, the act of neglecting), 过失 is used in professional and legal contexts for a mistake that has consequences.