Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water.
Chemically, fats are
triglycerides,
triesters of
glycerol and any of several
fatty acids. Fats may be either
solid or
liquid at
room temperature, depending on their structure and composition. Although the words "oils", "fats", and "
lipids" are all used to refer to fats, "oils" is usually used to refer to fats that are liquids at normal room temperature, while "fats" is usually used to refer to fats that are solids at normal room temperature. "Lipids" is used to refer to both liquid and solid fats, along with other related substances, usually in a medical or biochemical context. The word "
oil" is also used for any substance that does not mix with water and has a greasy feel, such as
petroleum,
heating oil, and
essential oils, regardless of its chemical structure.