Scientific name: avena sativa
Oats are a cereal crop grown mainly for turning into rolled oats and oatmeal for making porridge. It is also used as animal feed, particularly for horses.
Oil is a substance that is liquid at room temperature. Oil does not mix with water. Oil can be heated to much higher temperatures than water can, and so is useful in cooking food. Because oil does not stick to things, it is used to help stop food sticking when it is being cooked, and it helps stop parts of machinery like car engines from sticking together when they are running. Most oils will burn under the right conditions and can be used as a heat or light source, and a fuel to run things like internal combustion engines. Oil can be made from the seeds of many plants, as well as dug up from under the ground. Oil that comes from the ground used to be plants or animals many thousands of years ago, and had been changed into oil by the movement of the Earth.
Scientific name: olea europaea
Olives are the fruit of a small, slow-growing tree. They are originally from the Mediterranean region and grow best in poor soils in Mediterranean climates. Olives can be grown easily from both seeds and cuttings, but trees grown from seed don't always grow good fruit. Olives can't be eaten fresh from the tree, they are too bitter. Olives need to be prepared by soaking them in salty water or otherwise preparing them to be eaten. Some types of olive can be pressed and oil made from them.
An omelette is made from beaten eggs, cooked in a frying pan. A little milk or cream is often added to the eggs, and sometimes omelettes are made from only the white of the eggs, without the yolk. Omelettes may also contain added herbs, spices, diced vegetables or meat, particularly ham.
Scientific name: allium cepa
Onions are a vegetable. There are many different kinds of onions, ranging in size and colour from purple to red to white to green. Onions are used in almost every kind of food, raw or cooked. They can be very sharp when they are raw and many children do not like raw onions, but when they are cooked they are quite sweet.
Scientific name: citrus sinensis
An orange is the name for both a colour and a citrus fruit. Oranges are similar to lemons but are very sweet and can be eaten raw, squeezed to make juice, and can be made into marmalade. The colour orange can be made by mixing red and yellow paint.