Spoilage is the process of food going bad and becoming unsafe or unpleasant to eat. When milk sits too long in a warm kitchen, bacteria multiply and turn it sour. When bread develops fuzzy green mold, that's spoilage. Fresh strawberries might look perfect on Monday but turn mushy and smell strange by Friday.

Spoilage happens because tiny organisms like bacteria, mold, and yeast naturally break down food over time. Some signs of spoilage are obvious: a rotten smell, slimy texture, or visible mold. Other signs are subtler: meat changing color or vegetables becoming soft and wrinkled.

People invented refrigeration, canning, freezing, and drying specifically to slow or prevent spoilage. Before these methods existed, spoilage was a serious problem. Families had to eat food quickly or preserve it carefully, because wasted food meant wasted money and effort. Even today, grocery stores carefully monitor their products and remove items showing signs of spoilage before customers can buy them.

The word can also describe anything that deteriorates or becomes ruined over time, like the spoilage of untreated wood left outside in the rain.