What is the difference between baking, roasting and grilling?
How the heat reaches the food, and at what intensity — which determines what happens to the surface and the interior.
Baking and roasting both use an oven, and the distinction between them is largely convention rather than physics.
Roasting generally means higher temperatures applied to foods with existing structure — meat, whole vegetables — with the goal of browning the exterior while cooking through. Fat and juices are involved, and basting is common.
Baking generally means moderate temperatures applied to foods that set or rise during cooking — bread, cakes, pastry, gratins. The food changes structure as it cooks, which is why precision matters more.
The historical distinction was that roasting happened in front of an open fire on a spit, with radiant heat, while baking happened enclosed. When both moved into ovens, the terms stayed.
Grilling — where terminology diverges by country, and this causes real confusion.
In British usage, grilling means heat from above, from an overhead element. The American term is broiling.
In American usage, grilling means cooking over heat from below, on a barbecue or griddle. The British term for that is barbecuing.
A recipe saying "grill for five minutes" therefore means opposite things depending on where it was written, and it matters — one browns the top of a finished dish, the other cooks from beneath.
The heat transfer mechanisms, which explain the practical differences:
Convection — hot air circulating. Dominant in ovens, and why a fan oven cooks faster and more evenly, and why recipes specify a lower temperature for one.
Radiation — direct infrared from an element or flame. Dominant in grilling, which is why it browns surfaces quickly without cooking through, and why distance from the element is the main control.
Conduction — direct contact, from a tray, pan or griddle bars.
Why it matters in practice: grilling browns but does not cook thick items through; roasting does both but more slowly; and finishing a baked dish under a grill is the standard way to get colour without overcooking the interior.