Vegetable oils are triglycerides extracted from plants. Some of these oils have been part of human culture for millennia. Edible vegetable oils are used in food, both in cooking and as supplements. Many oils, edible and otherwise, are burned as fuel, such as in oil lamps and as a substitute for petroleum-based fuels. Some of the many other uses include wood finishing, oil painting, and skin care. Definition The term "vegetable oil" can be narrowly defined as referring only to substances that are liquid at room temperature, or broadly defined without regard to a substance's state (liquid or solid) at a given temperature. While a large majority of the entries in this list fit the narrower of these definitions, some do not qualify as vegetable oils according to all understandings of the term. Classification Vegetable oils can be classified in several ways. For instance, by their use or by the method used to extract them. In this article, vegetable oils are grouped in common classes of use. Extraction method There are several types of plant oils, distinguished by the method used to extract the oil from the plant. The relevant part of the plant may be placed under pressure to extract the oil, giving an expressed (or pressed) oil. The oils included in this list are of this type. Oils may also be extracted from plants by dissolving parts of plants in water or another solvent. The solution may be separated from the plant material and concentrated, giving an extracted or leached oil. The mixture may also be separated by distilling the oil away from the plant material. Oils extracted by this latter method are called essential oils. Essential oils often have different properties and uses than pressed or leached vegetable oils. Finally, macerated oils are made by infusing parts of plants in a base oil, a process called liquid–liquid extraction. Sources and Uses Most, but not all vegetable oils are extracted from the fruits or seeds of plants. For instance, palm oil is extracted from palm fruits, while soybean oil is extracted from soybean seeds. Vegetable oils may also be classified by grouping oils extracted from similar plants, such as "nut oils". Although most plants contain some oil, only the oil from certain major oil crops complemented by a few dozen minor oil crops is widely used and traded. Use Oils from plants are used for several different purposes.