To overcook is to apply heat for too long or at too high a temperature, damaging a food’s flavour, texture, colour, and nutritional value. Vegetables turn drab and mushy as cell walls collapse and chlorophyll degrades; meat toughens as proteins contract and squeeze out juices, then eventually shreds; eggs go rubbery and develop greenish yolks from iron-sulphur reactions; pasta turns to paste. Beyond sensory damage, overcooking destroys heat-sensitive vitamins, particularly vitamin C and folate, and can generate unwanted compounds such as acrylamide in browned starchy foods. The error usually stems from inattention, oversized portions that need staggered timing, or fear of undercooking. Skilled cooking is largely the discipline of stopping at the right moment: residual heat continues the process off the burner, so food should come out just before it looks done.