Porridge is a food made by heating or boiling ground, crushed or chopped starchy plants, typically grain, in milk or water. It is often cooked or served with added flavourings such as sugar, honey, fruit, or syrup to make a sweet cereal, or it can be mixed with spices, meat, or vegetables to make a savoury dish. It is usually served hot in a bowl, depending on its consistency. Oat porridge, or oatmeal, is one of the most common types of porridge. Gruel is a thinner version of porridge and congee is a savoury variation of porridge of Asian origin.

A grain is a small, hard, dry fruit (caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legumes.